Add pubsub to README
Merge pull request #259 from ryanseys/pubsub-readme

Add pubsub to README
readme: update link system, words, & ex. semantics

- Links from `[title](url)` to `[title][short-name]`.

- Add links to dev.google.com docs next to the product page links (ex: [Google Cloud Pub/Sub][cloud.google.com page] ([docs][dev.google.com page])

- Use more direct wording in pubsub example to illustrate the pulling logic behind listener creation & removal

-
docs: fixes #260 - give method sorting preferential treatment to ctors
storage: api refactor.
fix regression test linting.
update doc api versions.
readme: update with examples from storage.