I know this goes a bit against the contributing guidelines but it wasn't easy to split the work into smaller, independent PRs. I tried to keep the changes to the original codebase as small as possible and I'm open to other compatibility strategies if you don't like mine.
Added support for Python3 and Django1.5+, added tests
I noticed travis build fails because of django 1.4.0 is used as requirement but the six module was shipped only from the 1.4.2. If testing against 1.4.0 is a requirement I could add six as an external dependency, otherwise travis config file could be updated for using the latest 1.4.x
do not rely on backends order, fixed tox, bump django version on travis