Python 3 and django 1.5 compatability

This pull request does the following:

* Adds in Python 3.3+ compatibility with Python 2.7.x
* Adds in Django 1.5 custom user model compatibility while maintaining compatibility with Django 1.4 or less.
* Fixes some issues with DateField vs DateTimeField which broke hard on Python 3.

What this pull request doesn't do:

* There may be several DateField vs DateTimeField issues remaining. I'll investigate and possibly mitigate those in a future pull request.