pubsub: Adding docs to README.
Merge pull request #63 from silvolu/master

FIX(datastore regression tests): add missing index.yaml
datastore: Create query with optional namespace.
Merge pull request #65 from rakyll/createQuery

datastore: Create query with optional namespace
Merge pull request #42 from rakyll/pubsubdocs

pubsub: Adding docs to README
DOCS: add CONTRIBUTING.md