added travis continuous integration

These are small changes to get tests running with [travis-ci](http://travis-ci.org) whenever you commit to the repository. You get nice email notifications when tests fail, and reports like [this](https://travis-ci.org/edsu/htmldiff).

If you decide to use this pull request you'll want to s/edsu/cygri/ in the README.md so those links point at your repository.

If you are new to travis-ci.org let me know and I can give you instructions for getting started with it, but I imagine you can figure it out quickly.