Convert to py.test from nose

This is based on my settings_redux branch, but it converts the tests to py.test w/ pytest-django and moves the tests into the /tests folder. Reason for the conversion to py.test is that nose 1.x is in maintenance mode (https://mail.python.org/pipermail/python-announce-list/2014-March/010240.html)

I'll continue working on this PR to convert to factory boy as well which should take care of the horrible I've committed in videos.sampledata