Tests aren't actually testing various Django versions

I noticed that the buildout configuration was always hard-coding the Django version to 1.2.4. It wasn't actually running the tests under the different Django versions listed in the Travis CI configuration.

So I updated the testing to just use Django's `manage.py test` command. I also updated the Travis configuration so that it does actually install the various Django versions when running the tests. However, I'm now getting test failures in Django 1.4+.

Any chance I can get some help fixing up the tests so they pass in 1.4+?