Making testing sane.

I've added django-nose to the requirements and configured it.
Nose will auto-discover tests in many flavors.
Nose will do coverage checking (and style checking, and and and)
The usage is the same as before except now it works globally:

python manage.py test
python manage.py test apps/api
python manage.py test apps/web
python manage.py test apps/authenz
Merge branch 'master' into irjudson-test

Conflicts:
	codalab/apps/web/models.py
Merge pull request #177 from codalab/irjudson-test

Making tests work using django-nose, which enables many new features including test coverage and working hierarchical tests.