django 1.9 compatibility

[markvdb]

Hi,

For django 1.9, django.utils.importlib is deprecated. See https://docs.djangoproject.com/en/1.8/internals/deprecation/#deprecation-removed-in-1-9 . So ...
s/django.utils.importlib/importlib/ in at least billing/integration.py and billing/gateway.py ?

Probably lots more small things to fix than that, but I gave up after seeing braintree isn't supported anyway.

[theju]

There is a user who is working on it:
#132

[asgaines]

Furthermore, upon migrating, I receive the notification that IPAddressField has been deprecated. Support for it (except in historical migrations) will be removed in Django 1.9. I'm still using 1.8.

It suggests using GenericIPAddressField instead. Is this project being well maintained?