Clean up all imports

* Use relative imports within djrill package
* Standardize ordering
* Remove absolute_import (it's standard in all
  python versions we now support)

djrill/tests/mock_backend.py

@@ -1,7 +1,7 @@
 import json
-from mock import patch
 import requests
 import six
+from mock import patch
 
 from django.test import TestCase
 from django.test.utils import override_settings