Added a notifications app.

As this application's functionality will be spread between the frontend and a
celery instance, I needed a way to easily add notifications to the application
while not having the request handy. This is a simple bridge between those two,
it offers a message-like interface to add new notifications and it adds a
simple middleware that adds the notifications when needed.

Note that this has no unit-tests yet, that will come tomorrow or this weekend.
Start using the PyPI version of coveralls again.

Now that my fix was implemented in coveralls, I don't need to use my fork
anymore.