Python 2/3 port: stage2: all tests passing with Django 1.5.8 on Python 3.3 and Python 2.6/2.7.

All tests are now passing with Django 1.5.5 and Python 3.3 and Python 2.6/2.7.

Django 1.4.x has sloppier handling of unicode strings that are causing a few tests to fail still. I will release an updated version of the ``future`` package in the next few days that helps the tests to pass with Django 1.4.8 again too. (They are passing on my local machine, but there are a few bugs I'd like to squash before releasing the next version.)

This branch is now ready for wider testing. The biggest change is that every string used by Mezzanine is now unicode. This definitely calls for a new major version of Mezzanine.

Big thanks to <a href="http://pythoncharmers.com">Python Charmers</a> for supporting this work.