Merge pull request #115 from rakyll/experimental-pubsub

pubsub: Label pub sub client as experimental

README.md

@@ -375,12 +375,18 @@ bucket.copy(filename, { bucket: 'other-bucket', name: 'other-filename' }, callba
 bucket.remove(filename, callback);
 ~~~~
 
-### Google Cloud Pub/Sub
+### Google Cloud Pub/Sub (experimental)
 
 Google Cloud Pub/Sub is a reliable, many-to-many, asynchronous messaging
 service from Google Cloud Platform. A detailed overview is available on
 [Pub/Sub docs](https://developers.google.com/pubsub/overview).
 
+Note: Google Cloud Pub/Sub API is available as a Limited Preview and the
+client library we provide is currently experimental. The API and/or the
+client might be changed in backward-incompatible ways.
+This API is not subject to any SLA or deprecation policy. Request to be
+whitelisted to use it by filling the [Limited Preview application form](https://docs.google.com/a/google.com/forms/d/1IQY4LAbISLa86uxRv2dKAzkeWOyNZda_tUn7xgVYeoE/viewform).
+
 #### Configuration
 
 If you're running this client on Google Compute Engine, you need to construct