Add tox and travis-ci

- Added tox file
- Add travis.yml file, and tested it here: https://travis-ci.org/pconerly/rom
- Added `test-tox` to makefile.
- Added logic in `test_rom.py` to exit with the correct status code if either standard or lua-enabled tests failed.

@therealprologic, you're experienced with tox/travis, so let me know if there's anything I could change.

 @josiahcarlson let me know how this looks!