Eggify the project

I love `pyment.py` unfortunately you have to use the absolute path. Why not create a executable with setuptools. This way, you just have to run `python setup.py install` and voilà, you can run `pygement directory`.

I also added the test suite in setup.py, thus we can run `python setup.py test [TestCase[.test_case]]` to run the tests.

What do you think?