Node: add dev dependency on google-protobuf
diff --git a/package.json b/package.json
index 30d3251..5ed7f36 100644
--- a/package.json
+++ b/package.json
@@ -35,6 +35,7 @@
   "devDependencies": {
     "async": "^1.5.0",
     "google-auth-library": "^0.9.2",
+    "google-protobuf": "^3.0.0-alpha.5",
     "istanbul": "^0.3.21",
     "jsdoc": "^3.3.2",
     "jshint": "^2.5.0",