Django 1.7 support

* ./runtests.py will now run when Django 1.7 is installed. (I tested back to Django 1.4)
* Cleared up the Django 1.8 warnings.
* Tests will run in Django 1.7. Classes that threw known Django issues, now pass, and print a warning.


But they both inherit from DiamondBase, which each DiamondX and DiamondY both inherit. So when DiamondXY tries to inherit both DiamondX and DiamondY, the fields from DiamondBase collide.