In order to deprecate oauth2client:

1. Add support for google-auth to google-gax.
2. Add support for google-auth to google-cloud-python.
3. Add support for google-auth to google-api-python-client.
4. Release v1.0.0.
5. Figure out a story for obtaining user auth credentials (oauthlib integration?).
6. Update auth documentation on developers.google.com and cloud.google.com to point to google-auth.

Am I forgetting anything?