Update dependencies, enable pruning for vendor/

So, `dep` got an nice new feature to remove tests and non-go files from
`vendor/`, and this brings the size of the vendor directory from ~300MiB
down to ~20MiB. We don that now.

vendor/bazil.org/fuse/fuse.go

@@ -1262,6 +1262,7 @@ func (r *StatfsRequest) Respond(resp *StatfsResponse) {
 		Bfree:   resp.Bfree,
 		Bavail:  resp.Bavail,
 		Files:   resp.Files,
+		Ffree:   resp.Ffree,
 		Bsize:   resp.Bsize,
 		Namelen: resp.Namelen,
 		Frsize:  resp.Frsize,