Fixed testing, fixed python3 compatibility, added classifiers for PyPI

- Made it possible to run `python manage.py test` and get passing tests
- Added a `.travis.yml` file to enable Travis CI builds
- Fixed Python 3 compatibility without compromising Django 1.4 compatibility
- Added trove classifiers to `setup.py` for PyPI
Sorry just noticed that you moved the location of `settings.py` from `django_user_agents/tests` directory to `django_user_agents`. I'd rather keep the `settings.py` within the `tests` folder. Could you move it back to where it was?

You can then add something like `--settings=django_user_agents.tests.settings` (make sure it's the correct path) to `.travis.yml`.

Also, feel free to add yourself to `AUTHORS.txt` :)

Sorry for being fussy and thanks again for the PR!