vendor dependencies with godep

dependencies are vendored into Godeps/_workspace and commit versions are
recorded in Godeps.json

update datastore to e89f0511
update go.crypto

blocks.go

 package blocks
 
 import (
+	mh "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multihash"
 	u "github.com/jbenet/go-ipfs/util"
-	mh "github.com/jbenet/go-multihash"
 )
 
 // Block is the ipfs blocks service. It is the way