update to newer ipld node interface with Copy and better Tree

License: MIT
Signed-off-by: Jeromy <why@ipfs.io>

interface.go

@@ -5,8 +5,8 @@ import (
 	"errors"
 	"io"
 
-	ipld "gx/ipfs/QmU7bFWQ793qmvNy7outdCaMfSDNk8uqhx4VNrxYj5fj5g/go-ipld-node"
-	cid "gx/ipfs/QmXfiyr2RWEXpVDdaYnD2HNiBk6UBddsvEP4RPfXb6nGqY/go-cid"
+	ipld "gx/ipfs/QmUsVJ7AEnGyjX8YWnrwq9vmECVGwBQNAKPpgz5KSg8dcq/go-ipld-node"
+	cid "gx/ipfs/QmcEcrBAMrwMyhSjXt4yfyPpzgSuV8HLHavnfmiKCSRqZU/go-cid"
 )
 
 // type CoreAPI interface {