Travis CI support

This allows for tests to run automatically on every push via Travis CI. Depends on #1.

If you haven't used Travis CI, a brief explanation follows.

Once merged into the main repository, you would have to create an account on the [Travis CI website](https://travis-ci.org/). After doing that and turning on builds for this repo, they will be run automatically on every push. You can also configure tests to run for [every pull request](http://about.travis-ci.org/blog/2012-09-04-pull-requests-just-got-even-more-awesome/).

You can also add a nice build status indicator with the following Markdown:

    [![Build Status](https://travis-ci.org/craigbruce/django-oauth.png)](https://travis-ci.org/craigbruce/django-oauth)