setup.py: Don't install_require South
setup.py: Don't install_require South

Some projects might not want it.

whyflyru/django-iprestrict,whyflyru/django-iprestrict,muccg/django-iprestrict,whyflyru/django-iprestrict,muccg/django-iprestrict,whyflyru/django-iprestrict,muccg/django-iprestrict