Test with Travis-CI

This doesn't actually add any tests; it's a first step towards #42. (Ondrej had some tests from a while back that he added, so I've moved them to the new `app/test` subdirectory.)

What this does do is:

- Install dependencies
- Install the App Engine SDK
- Start the SDK server
- Run Python unittests through Nose

Tasks:

- [ ] Run PhantomJS/CasperJS tests
- [ ] (maybe) Deploy to App Engine automatically