Django-libs

- Added JSONResponseMixin as suggested in the official Django docs

- Added new method ``get_data_payload`` to ``ViewTestMixin`` that allows you
to call all your views with given POST or GET data. (See docs)

- Changed test_settings.py so that only 'admin.py$' files are excluded from
coverage. Before this change, an app with the name 'foobar_admin' would
be completely excluded from coverage, which is bad.

- Added test mixins to ease the process of writing integration tests with
self.client.get. See the docs for further explanation.

- Added custom testrunner (see docs/testrunner.rst)

- Initial commit