Bump django dependency to 1.7.13.

Picking up the latest security release for Django.
Use 'cvs version' instead of 'cvs rls' to test remote repositories.

'cvs rls' is only available in CVS 1.12+, which isn't yet considered stable.
Fortunately, if 'cvs version' is run with a CVSROOT, it will end up checking
whether that CVSROOT is valid, which is perfect for our needs.

Testing done: Ran unit tests.

Fixes bug 3343.

Reviewed at https://reviews.reviewboard.org/r/5831/