Fix #195: Add support for Python 3.2 and 3.3 and enable tests on them.

Thanks to @senden9 for most of these fixes.
Use Django's version of six and drop Django 1.3 support.

Django 1.3 lacks a decorator we want to use for Python 3 support, and
given that 1.3 is out-of-date and we already have a few workarounds in
place to keep it working, it's time to drop it. This includes removing
the workarounds I know of to clean up the code a bit.