Releases could be improved

[bsiegert]

Currently, google-apitools releases do not contain any changelog, and it is hard to see what the actual changes between two versions are. When you tag a release, it would be nice if that could be added.

Also, if you click on "Releases" in the github UI, it pretends that 0.5.16 (which it calls "HttpError Class") is the latest release.

This would make it easier to maintain OS packages of google-apitools, like for example http://pkgsrc.se/www/py-google-apitools :)