Python 3.3 compatibility.

Conflicts:
	state_machine/models/__init__.py
	state_machine/orm/base.py
Add classifiers.

Classifiers are important to signify Python 3 compatibility, and are used by
 + PyPI's [Python 3 Package List](https://pypi.python.org/pypi?:action=browse&c=533&show=all), and
 + [caniusepython3.com](http://caniusepython3.com)

Conflicts:
	setup.py
Make setup.py test run tests, include tox.ini to test in multiple environments.

Conflicts:
	setup.py
Test SQLAlchemy by default, as it uses an in memory SQLite DB (as opposed to MongoDB, which requires an external server.
Add tox support for separately testing mongo support. Doesn't run by default in case people don't have a local running mongo server.
Add travis support
Merge pull request #11 from daxtens/feature/tests

Run tests on Python 3.3/2.7/PyPy with Tox, run tests on Travis