Fix tests that are broken under Python 2.7.

In Python 2.7, the unittest module was revamped to match the Python 3 version. Python 2.7 unittest doesn't run class fixtures if the class method isn't named setUpClass(). This fixes the tests that throw AttributeError under Python 2.7 (also mentioned in Issues #20 and #62):
> "AttributeError: 'TestGit' object has no attribute 'rorepo'"

I also tested under Python 2.6 to ensure that those tests would still run. I have a similar patch incoming on master.