Update runtests.py for Django 1.5 compatibility.

The Django integration tests were failing to run against Django 1.5 because they used test API that's been deprecated since Django 1.3 and was removed in 1.5, and DATABASES setting syntax that's been deprecated I think since 1.2?

I updated both of these and the tests now run and pass against Django 1.5.1, 1.4.5, and 1.3.7. This pull request means the tests will no longer run against Django 1.2 or earlier (not that I tested whether they did previously).