WIP -- Django 1.9 and drf 3.3.x support

[auvipy]

No description provided.

[nemesifier]

👍 thanks @auvipy, when you are done please squash the commits

[nemesifier]

If you could also clean up some lines that were introduced to maintain compatibility with old python & django versions would be really helpful, eg:

• https://github.com/djangonauts/django-rest-framework-gis/blob/master/rest_framework_gis/apps.py
• https://github.com/djangonauts/django-rest-framework-gis/blob/master/rest_framework_gis/utils.py
• https://github.com/djangonauts/django-rest-framework-gis/blob/master/rest_framework_gis/__init__.py#L19-L41

[auvipy]

I was waiting for your feedback and will do what you suggested.