Remove Travis environments

These are no longer needed after the changes made in f9e3a3f.
Additional testing clean up

Coverage is now a testing requirement. Also, both tox and Travis CI and now configured to call `nosetests` directly and test PyPy.

The `assertIn()` call has been replaced by an `assertTrue()` call so that Python 2.6 can run the tests without `unittest2`.

And finally the `setup.py` script is being cleaned up a little.