Fix drf and django filter versions.

Issue: ImportError: Could not import 'rest_framework.filters.DjangoFilterBackend'

DRF-3.7.0 has removed DjangoFilterBackend, if we want to move to DRF-3.7.0, we shall be using 'django_filters.rest_framework.DjangoFilterBackend' instead.

requirements.txt

 ## NOTE: This is not a working req file -- merely a collection for notes.
 django==1.9
-djangorestframework
+djangorestframework==3.6.4
 django-cors-headers
 django-oauth-toolkit==0.11.0
-django-filter
+django-filter==1.0.4
 newrelic
 uwsgi
 pysftp