Fix #475: Remove Django from install_requires
Fix #475: Remove Django from install_requires

Also remove the tests_require entry which is completely unused.

emilhdiaz/django-mptt,matthiask/django-mptt,emilhdiaz/django-mptt,emilhdiaz/django-mptt,matthiask/django-mptt,emilhdiaz/django-mptt,matthiask/django-mptt,matthiask/django-mptt