Proper setup for local testing of hello world (#772)

* Proper setup for local testing of hello world

* Update README.md

Author: kenahrens

functions/helloworld/README.md

@@ -18,10 +18,21 @@ See the [Cloud Functions Hello World tutorial][tutorial].
 
 1. Read and follow the [prerequisites](../../../../#prerequisites).
 
+1. Install and run the [Google Cloud Functions Emulator](https://github.com/GoogleCloudPlatform/cloud-functions-emulator)
+
+        npm install -g @google-cloud/functions-emulator
+        functions start
+
 1. Install dependencies:
 
         npm install
 
+1. Set the following environment variables:
+
+        export GCF_REGION=us-central1
+        export FUNCTIONS_TOPIC=[YOUR_PUBSUB_TOPIC]
+        export FUNCTIONS_BUCKET=[YOUR_CLOUD_STORAGE_BUCKET]
+
 1. Run the tests:
 
         npm test

functions/helloworld/package.json

@@ -25,7 +25,6 @@
     "safe-buffer": "5.1.1"
   },
   "devDependencies": {
-    "@google-cloud/functions-emulator": "^1.0.0-beta.5",
     "@google-cloud/nodejs-repo-tools": "^2.2.5",
     "@google-cloud/pubsub": "^0.17.0",
     "@google-cloud/storage": "^1.5.0",
@@ -43,9 +42,10 @@
     "requiresProjectId": true,
     "requiredEnvVars": [
       "BASE_URL",
+      "GCLOUD_PROJECT",
       "GCF_REGION",
-      "TOPIC",
-      "BUCKET",
+      "FUNCTIONS_TOPIC",
+      "FUNCTIONS_BUCKET",
       "FUNCTIONS_CMD"
     ]
   }