chore: update CONTRIBUTING.md and make releaseType node (#250)

Author: Benjamin E. Coe

packages/google-cloud-automl/CONTRIBUTING.md

@@ -47,11 +47,12 @@ accept your pull requests.
 
 1.  Run the tests:
 
-        # Run all tests.
+        # Run unit tests.
         npm test
 
-        # Run all unit tests.
-        npm run test-only
+        # Run sample integration tests.
+        gcloud auth application-default login
+        npm run samples-test
 
         # Run all system tests.
         gcloud auth application-default login