First version of python 3 support

Hey there, I was using fig for a project using Python3 and I thought I do my best to add support for running it on all major platforms.

At least the tests run on python 2.6-3.3 now and the rest seems to work too.

I also changed the way tests are running, removing ``requirements*.txt`` and relying on ``setup.py test`` - calling ``nosetests`` still works but in my experience it feels more natural this way.

Let me know what you think.

Cheers!