diff --git a/vendor/github.com/peterbourgon/diskv/diskv.go b/vendor/github.com/peterbourgon/diskv/diskv.go
new file mode 100644
index 0000000..524dc0a
--- /dev/null
+++ b/vendor/github.com/peterbourgon/diskv/diskv.go
@@ -0,0 +1,624 @@
+// Diskv (disk-vee) is a simple, persistent, key-value store.
+// It stores all data flatly on the filesystem.
+
+package diskv
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"syscall"
+)
+
+const (
+	defaultBasePath             = "diskv"
+	defaultFilePerm os.FileMode = 0666
+	defaultPathPerm os.FileMode = 0777
+)
+
+var (
+	defaultTransform   = func(s string) []string { return []string{} }
+	errCanceled        = errors.New("canceled")
+	errEmptyKey        = errors.New("empty key")
+	errBadKey          = errors.New("bad key")
+	errImportDirectory = errors.New("can't import a directory")
+)
+
+// TransformFunction transforms a key into a slice of strings, with each
+// element in the slice representing a directory in the file path where the
+// key's entry will eventually be stored.
+//
+// For example, if TransformFunc transforms "abcdef" to ["ab", "cde", "f"],
+// the final location of the data file will be <basedir>/ab/cde/f/abcdef
+type TransformFunction func(s string) []string
+
+// Options define a set of properties that dictate Diskv behavior.
+// All values are optional.
+type Options struct {
+	BasePath     string
+	Transform    TransformFunction
+	CacheSizeMax uint64 // bytes
+	PathPerm     os.FileMode
+	FilePerm     os.FileMode
+	// If TempDir is set, it will enable filesystem atomic writes by
+	// writing temporary files to that location before being moved
+	// to BasePath.
+	// Note that TempDir MUST be on the same device/partition as
+	// BasePath.
+	TempDir string
+
+	Index     Index
+	IndexLess LessFunction
+
+	Compression Compression
+}
+
+// Diskv implements the Diskv interface. You shouldn't construct Diskv
+// structures directly; instead, use the New constructor.
+type Diskv struct {
+	Options
+	mu        sync.RWMutex
+	cache     map[string][]byte
+	cacheSize uint64
+}
+
+// New returns an initialized Diskv structure, ready to use.
+// If the path identified by baseDir already contains data,
+// it will be accessible, but not yet cached.
+func New(o Options) *Diskv {
+	if o.BasePath == "" {
+		o.BasePath = defaultBasePath
+	}
+	if o.Transform == nil {
+		o.Transform = defaultTransform
+	}
+	if o.PathPerm == 0 {
+		o.PathPerm = defaultPathPerm
+	}
+	if o.FilePerm == 0 {
+		o.FilePerm = defaultFilePerm
+	}
+
+	d := &Diskv{
+		Options:   o,
+		cache:     map[string][]byte{},
+		cacheSize: 0,
+	}
+
+	if d.Index != nil && d.IndexLess != nil {
+		d.Index.Initialize(d.IndexLess, d.Keys(nil))
+	}
+
+	return d
+}
+
+// Write synchronously writes the key-value pair to disk, making it immediately
+// available for reads. Write relies on the filesystem to perform an eventual
+// sync to physical media. If you need stronger guarantees, see WriteStream.
+func (d *Diskv) Write(key string, val []byte) error {
+	return d.WriteStream(key, bytes.NewBuffer(val), false)
+}
+
+// WriteStream writes the data represented by the io.Reader to the disk, under
+// the provided key. If sync is true, WriteStream performs an explicit sync on
+// the file as soon as it's written.
+//
+// bytes.Buffer provides io.Reader semantics for basic data types.
+func (d *Diskv) WriteStream(key string, r io.Reader, sync bool) error {
+	if len(key) <= 0 {
+		return errEmptyKey
+	}
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	return d.writeStreamWithLock(key, r, sync)
+}
+
+// createKeyFileWithLock either creates the key file directly, or
+// creates a temporary file in TempDir if it is set.
+func (d *Diskv) createKeyFileWithLock(key string) (*os.File, error) {
+	if d.TempDir != "" {
+		if err := os.MkdirAll(d.TempDir, d.PathPerm); err != nil {
+			return nil, fmt.Errorf("temp mkdir: %s", err)
+		}
+		f, err := ioutil.TempFile(d.TempDir, "")
+		if err != nil {
+			return nil, fmt.Errorf("temp file: %s", err)
+		}
+
+		if err := f.Chmod(d.FilePerm); err != nil {
+			f.Close()           // error deliberately ignored
+			os.Remove(f.Name()) // error deliberately ignored
+			return nil, fmt.Errorf("chmod: %s", err)
+		}
+		return f, nil
+	}
+
+	mode := os.O_WRONLY | os.O_CREATE | os.O_TRUNC // overwrite if exists
+	f, err := os.OpenFile(d.completeFilename(key), mode, d.FilePerm)
+	if err != nil {
+		return nil, fmt.Errorf("open file: %s", err)
+	}
+	return f, nil
+}
+
+// writeStream does no input validation checking.
+func (d *Diskv) writeStreamWithLock(key string, r io.Reader, sync bool) error {
+	if err := d.ensurePathWithLock(key); err != nil {
+		return fmt.Errorf("ensure path: %s", err)
+	}
+
+	f, err := d.createKeyFileWithLock(key)
+	if err != nil {
+		return fmt.Errorf("create key file: %s", err)
+	}
+
+	wc := io.WriteCloser(&nopWriteCloser{f})
+	if d.Compression != nil {
+		wc, err = d.Compression.Writer(f)
+		if err != nil {
+			f.Close()           // error deliberately ignored
+			os.Remove(f.Name()) // error deliberately ignored
+			return fmt.Errorf("compression writer: %s", err)
+		}
+	}
+
+	if _, err := io.Copy(wc, r); err != nil {
+		f.Close()           // error deliberately ignored
+		os.Remove(f.Name()) // error deliberately ignored
+		return fmt.Errorf("i/o copy: %s", err)
+	}
+
+	if err := wc.Close(); err != nil {
+		f.Close()           // error deliberately ignored
+		os.Remove(f.Name()) // error deliberately ignored
+		return fmt.Errorf("compression close: %s", err)
+	}
+
+	if sync {
+		if err := f.Sync(); err != nil {
+			f.Close()           // error deliberately ignored
+			os.Remove(f.Name()) // error deliberately ignored
+			return fmt.Errorf("file sync: %s", err)
+		}
+	}
+
+	if err := f.Close(); err != nil {
+		return fmt.Errorf("file close: %s", err)
+	}
+
+	if f.Name() != d.completeFilename(key) {
+		if err := os.Rename(f.Name(), d.completeFilename(key)); err != nil {
+			os.Remove(f.Name()) // error deliberately ignored
+			return fmt.Errorf("rename: %s", err)
+		}
+	}
+
+	if d.Index != nil {
+		d.Index.Insert(key)
+	}
+
+	d.bustCacheWithLock(key) // cache only on read
+
+	return nil
+}
+
+// Import imports the source file into diskv under the destination key. If the
+// destination key already exists, it's overwritten. If move is true, the
+// source file is removed after a successful import.
+func (d *Diskv) Import(srcFilename, dstKey string, move bool) (err error) {
+	if dstKey == "" {
+		return errEmptyKey
+	}
+
+	if fi, err := os.Stat(srcFilename); err != nil {
+		return err
+	} else if fi.IsDir() {
+		return errImportDirectory
+	}
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if err := d.ensurePathWithLock(dstKey); err != nil {
+		return fmt.Errorf("ensure path: %s", err)
+	}
+
+	if move {
+		if err := syscall.Rename(srcFilename, d.completeFilename(dstKey)); err == nil {
+			d.bustCacheWithLock(dstKey)
+			return nil
+		} else if err != syscall.EXDEV {
+			// If it failed due to being on a different device, fall back to copying
+			return err
+		}
+	}
+
+	f, err := os.Open(srcFilename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	err = d.writeStreamWithLock(dstKey, f, false)
+	if err == nil && move {
+		err = os.Remove(srcFilename)
+	}
+	return err
+}
+
+// Read reads the key and returns the value.
+// If the key is available in the cache, Read won't touch the disk.
+// If the key is not in the cache, Read will have the side-effect of
+// lazily caching the value.
+func (d *Diskv) Read(key string) ([]byte, error) {
+	rc, err := d.ReadStream(key, false)
+	if err != nil {
+		return []byte{}, err
+	}
+	defer rc.Close()
+	return ioutil.ReadAll(rc)
+}
+
+// ReadStream reads the key and returns the value (data) as an io.ReadCloser.
+// If the value is cached from a previous read, and direct is false,
+// ReadStream will use the cached value. Otherwise, it will return a handle to
+// the file on disk, and cache the data on read.
+//
+// If direct is true, ReadStream will lazily delete any cached value for the
+// key, and return a direct handle to the file on disk.
+//
+// If compression is enabled, ReadStream taps into the io.Reader stream prior
+// to decompression, and caches the compressed data.
+func (d *Diskv) ReadStream(key string, direct bool) (io.ReadCloser, error) {
+	d.mu.RLock()
+	defer d.mu.RUnlock()
+
+	if val, ok := d.cache[key]; ok {
+		if !direct {
+			buf := bytes.NewBuffer(val)
+			if d.Compression != nil {
+				return d.Compression.Reader(buf)
+			}
+			return ioutil.NopCloser(buf), nil
+		}
+
+		go func() {
+			d.mu.Lock()
+			defer d.mu.Unlock()
+			d.uncacheWithLock(key, uint64(len(val)))
+		}()
+	}
+
+	return d.readWithRLock(key)
+}
+
+// read ignores the cache, and returns an io.ReadCloser representing the
+// decompressed data for the given key, streamed from the disk. Clients should
+// acquire a read lock on the Diskv and check the cache themselves before
+// calling read.
+func (d *Diskv) readWithRLock(key string) (io.ReadCloser, error) {
+	filename := d.completeFilename(key)
+
+	fi, err := os.Stat(filename)
+	if err != nil {
+		return nil, err
+	}
+	if fi.IsDir() {
+		return nil, os.ErrNotExist
+	}
+
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	var r io.Reader
+	if d.CacheSizeMax > 0 {
+		r = newSiphon(f, d, key)
+	} else {
+		r = &closingReader{f}
+	}
+
+	var rc = io.ReadCloser(ioutil.NopCloser(r))
+	if d.Compression != nil {
+		rc, err = d.Compression.Reader(r)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return rc, nil
+}
+
+// closingReader provides a Reader that automatically closes the
+// embedded ReadCloser when it reaches EOF
+type closingReader struct {
+	rc io.ReadCloser
+}
+
+func (cr closingReader) Read(p []byte) (int, error) {
+	n, err := cr.rc.Read(p)
+	if err == io.EOF {
+		if closeErr := cr.rc.Close(); closeErr != nil {
+			return n, closeErr // close must succeed for Read to succeed
+		}
+	}
+	return n, err
+}
+
+// siphon is like a TeeReader: it copies all data read through it to an
+// internal buffer, and moves that buffer to the cache at EOF.
+type siphon struct {
+	f   *os.File
+	d   *Diskv
+	key string
+	buf *bytes.Buffer
+}
+
+// newSiphon constructs a siphoning reader that represents the passed file.
+// When a successful series of reads ends in an EOF, the siphon will write
+// the buffered data to Diskv's cache under the given key.
+func newSiphon(f *os.File, d *Diskv, key string) io.Reader {
+	return &siphon{
+		f:   f,
+		d:   d,
+		key: key,
+		buf: &bytes.Buffer{},
+	}
+}
+
+// Read implements the io.Reader interface for siphon.
+func (s *siphon) Read(p []byte) (int, error) {
+	n, err := s.f.Read(p)
+
+	if err == nil {
+		return s.buf.Write(p[0:n]) // Write must succeed for Read to succeed
+	}
+
+	if err == io.EOF {
+		s.d.cacheWithoutLock(s.key, s.buf.Bytes()) // cache may fail
+		if closeErr := s.f.Close(); closeErr != nil {
+			return n, closeErr // close must succeed for Read to succeed
+		}
+		return n, err
+	}
+
+	return n, err
+}
+
+// Erase synchronously erases the given key from the disk and the cache.
+func (d *Diskv) Erase(key string) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	d.bustCacheWithLock(key)
+
+	// erase from index
+	if d.Index != nil {
+		d.Index.Delete(key)
+	}
+
+	// erase from disk
+	filename := d.completeFilename(key)
+	if s, err := os.Stat(filename); err == nil {
+		if s.IsDir() {
+			return errBadKey
+		}
+		if err = os.Remove(filename); err != nil {
+			return err
+		}
+	} else {
+		// Return err as-is so caller can do os.IsNotExist(err).
+		return err
+	}
+
+	// clean up and return
+	d.pruneDirsWithLock(key)
+	return nil
+}
+
+// EraseAll will delete all of the data from the store, both in the cache and on
+// the disk. Note that EraseAll doesn't distinguish diskv-related data from non-
+// diskv-related data. Care should be taken to always specify a diskv base
+// directory that is exclusively for diskv data.
+func (d *Diskv) EraseAll() error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	d.cache = make(map[string][]byte)
+	d.cacheSize = 0
+	if d.TempDir != "" {
+		os.RemoveAll(d.TempDir) // errors ignored
+	}
+	return os.RemoveAll(d.BasePath)
+}
+
+// Has returns true if the given key exists.
+func (d *Diskv) Has(key string) bool {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if _, ok := d.cache[key]; ok {
+		return true
+	}
+
+	filename := d.completeFilename(key)
+	s, err := os.Stat(filename)
+	if err != nil {
+		return false
+	}
+	if s.IsDir() {
+		return false
+	}
+
+	return true
+}
+
+// Keys returns a channel that will yield every key accessible by the store,
+// in undefined order. If a cancel channel is provided, closing it will
+// terminate and close the keys channel.
+func (d *Diskv) Keys(cancel <-chan struct{}) <-chan string {
+	return d.KeysPrefix("", cancel)
+}
+
+// KeysPrefix returns a channel that will yield every key accessible by the
+// store with the given prefix, in undefined order. If a cancel channel is
+// provided, closing it will terminate and close the keys channel. If the
+// provided prefix is the empty string, all keys will be yielded.
+func (d *Diskv) KeysPrefix(prefix string, cancel <-chan struct{}) <-chan string {
+	var prepath string
+	if prefix == "" {
+		prepath = d.BasePath
+	} else {
+		prepath = d.pathFor(prefix)
+	}
+	c := make(chan string)
+	go func() {
+		filepath.Walk(prepath, walker(c, prefix, cancel))
+		close(c)
+	}()
+	return c
+}
+
+// walker returns a function which satisfies the filepath.WalkFunc interface.
+// It sends every non-directory file entry down the channel c.
+func walker(c chan<- string, prefix string, cancel <-chan struct{}) filepath.WalkFunc {
+	return func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if info.IsDir() || !strings.HasPrefix(info.Name(), prefix) {
+			return nil // "pass"
+		}
+
+		select {
+		case c <- info.Name():
+		case <-cancel:
+			return errCanceled
+		}
+
+		return nil
+	}
+}
+
+// pathFor returns the absolute path for location on the filesystem where the
+// data for the given key will be stored.
+func (d *Diskv) pathFor(key string) string {
+	return filepath.Join(d.BasePath, filepath.Join(d.Transform(key)...))
+}
+
+// ensurePathWithLock is a helper function that generates all necessary
+// directories on the filesystem for the given key.
+func (d *Diskv) ensurePathWithLock(key string) error {
+	return os.MkdirAll(d.pathFor(key), d.PathPerm)
+}
+
+// completeFilename returns the absolute path to the file for the given key.
+func (d *Diskv) completeFilename(key string) string {
+	return filepath.Join(d.pathFor(key), key)
+}
+
+// cacheWithLock attempts to cache the given key-value pair in the store's
+// cache. It can fail if the value is larger than the cache's maximum size.
+func (d *Diskv) cacheWithLock(key string, val []byte) error {
+	valueSize := uint64(len(val))
+	if err := d.ensureCacheSpaceWithLock(valueSize); err != nil {
+		return fmt.Errorf("%s; not caching", err)
+	}
+
+	// be very strict about memory guarantees
+	if (d.cacheSize + valueSize) > d.CacheSizeMax {
+		panic(fmt.Sprintf("failed to make room for value (%d/%d)", valueSize, d.CacheSizeMax))
+	}
+
+	d.cache[key] = val
+	d.cacheSize += valueSize
+	return nil
+}
+
+// cacheWithoutLock acquires the store's (write) mutex and calls cacheWithLock.
+func (d *Diskv) cacheWithoutLock(key string, val []byte) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	return d.cacheWithLock(key, val)
+}
+
+func (d *Diskv) bustCacheWithLock(key string) {
+	if val, ok := d.cache[key]; ok {
+		d.uncacheWithLock(key, uint64(len(val)))
+	}
+}
+
+func (d *Diskv) uncacheWithLock(key string, sz uint64) {
+	d.cacheSize -= sz
+	delete(d.cache, key)
+}
+
+// pruneDirsWithLock deletes empty directories in the path walk leading to the
+// key k. Typically this function is called after an Erase is made.
+func (d *Diskv) pruneDirsWithLock(key string) error {
+	pathlist := d.Transform(key)
+	for i := range pathlist {
+		dir := filepath.Join(d.BasePath, filepath.Join(pathlist[:len(pathlist)-i]...))
+
+		// thanks to Steven Blenkinsop for this snippet
+		switch fi, err := os.Stat(dir); true {
+		case err != nil:
+			return err
+		case !fi.IsDir():
+			panic(fmt.Sprintf("corrupt dirstate at %s", dir))
+		}
+
+		nlinks, err := filepath.Glob(filepath.Join(dir, "*"))
+		if err != nil {
+			return err
+		} else if len(nlinks) > 0 {
+			return nil // has subdirs -- do not prune
+		}
+		if err = os.Remove(dir); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// ensureCacheSpaceWithLock deletes entries from the cache in arbitrary order
+// until the cache has at least valueSize bytes available.
+func (d *Diskv) ensureCacheSpaceWithLock(valueSize uint64) error {
+	if valueSize > d.CacheSizeMax {
+		return fmt.Errorf("value size (%d bytes) too large for cache (%d bytes)", valueSize, d.CacheSizeMax)
+	}
+
+	safe := func() bool { return (d.cacheSize + valueSize) <= d.CacheSizeMax }
+
+	for key, val := range d.cache {
+		if safe() {
+			break
+		}
+
+		d.uncacheWithLock(key, uint64(len(val)))
+	}
+
+	if !safe() {
+		panic(fmt.Sprintf("%d bytes still won't fit in the cache! (max %d bytes)", valueSize, d.CacheSizeMax))
+	}
+
+	return nil
+}
+
+// nopWriteCloser wraps an io.Writer and provides a no-op Close method to
+// satisfy the io.WriteCloser interface.
+type nopWriteCloser struct {
+	io.Writer
+}
+
+func (wc *nopWriteCloser) Write(p []byte) (int, error) { return wc.Writer.Write(p) }
+func (wc *nopWriteCloser) Close() error                { return nil }