django-mongokit now compatible with Django 1.4

I've finally had time to sort out the django-mongokit code so it's now fully compatible with Django 1.4.

Because I don't personally use the project I've sort of got myself lost in various patches from some awesome contributors who keep it in check.

Also, thanks to Marc Abramowitz who added a tox.ini which I've now updated to also test python 2.7 and Django 1.4

Go forth and build awesome Django apps with MongoKit which is still think is the best wrapper available on PyMongo out there.