Merge pull request #4166 from murgatroid99/node_0.12.0_version_bump

Updated Node package version to 0.12.0

package.json

 {
   "name": "grpc",
-  "version": "0.11.1",
+  "version": "0.12.0",
   "author": "Google Inc.",
   "description": "gRPC Library for Node",
   "homepage": "http://www.grpc.io/",