Allow Travis to build wheels and attach them to releases

[rosskarchner]

This was primarirly accomplished using the travis cli too:

travis setup releases

... And adding some code to make sure sure a wheel gets generated as part of the build process (including adding config for Node 6, bower, and gulp)

I also added 'setuptools-git-version' to setup.py, which will allow setuptools to infer the version number from the git tag

[coveralls]

Coverage remained the same at 97.933% when pulling 84ee0ca on travis-build-my-wheel into cf01aa0 on master.

[coveralls]

Coverage remained the same at 97.933% when pulling 23cba38 on travis-build-my-wheel into cf01aa0 on master.

[coveralls]

Coverage remained the same at 97.933% when pulling ca30337 on travis-build-my-wheel into cf01aa0 on master.

[higs4281]

This makes a person want to generate a release!

Unrelated to this PR, but I wonder if we should move satellites away from coveralls to follow the mother ship.

[rosskarchner]

@higs4281 someone ought to test it out-- go for it!

The attachment will take a few minutes to show up, but you should be able to monitor progress at https://travis-ci.org/cfpb/retirement