merkledag: fix json marshalling of pbnode

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

node.go

@@ -2,6 +2,7 @@ package merkledag
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 
 	node "gx/ipfs/QmRSU5EqqWVZSNdbU51yXmVoF1uNw3JgTNB6RaiL7DZM16/go-ipld-node"
@@ -228,6 +229,15 @@ func (n *ProtoNode) Loggable() map[string]interface{} {
 	}
 }
 
+func (n *ProtoNode) MarshalJSON() ([]byte, error) {
+	out := map[string]interface{}{
+		"data":  n.data,
+		"links": n.links,
+	}
+
+	return json.Marshal(out)
+}
+
 func (n *ProtoNode) Cid() *cid.Cid {
 	if n.encoded != nil && n.cached != nil {
 		return n.cached