Change Fourth Wall to be a Django 1.7.1 project

This commit uses the [Heroku Django template][1] to create a Django 1.7.1
project for Fourth Wall.

At the moment this is just the existing code moved around to fit in a
Django application. My intention is to move this away from being an
entirely client-side application into something where configuration
is stored in a database and the application is hosted using a service
like Heroku.

Lots of people who have used this project have struggled with using Gists
for configuration, because of GitHub's model where multiple people can't
edit a single Gist.

I've removed the tests because they're using a version of Jasmine that
was released in December 2012 and I think there are better ways of doing
things now.

[1]: https://github.com/heroku/heroku-django-template
Move repository config into Django settings

Remove all of the JavaScript related to fetching a Gist or a file
from GitHub, and instead add the `/repos` endpoint in this app to
control which repos are displayed.
Expose repositories from the database

Store repositories in the database and allow editing of them with
the Django admin interface.
Always return a baseUrl from the repos endpoint

Instead of defaulting this in JavaScript, just always return this
key/value pair in the JSON.
Use python-social-auth to login with GitHub

This commit adds authentication with GitHub and GitHub Enterprise
using python-social-auth.

The flow isn't perfect yet but I'm pretty happy with it:

- You must sign in with GitHub (public) first
- You can only sign in to GitHub Enterprise if you're signed in to
  GitHub already
- If you're signed in to GitHub and you sign in to GitHub Enterprise,
  your 2 tokens are associated with the same account in the database.

Tokens are returned in the list of repositories, and the JavaScript
has been updated to use those tokens rather than try and pry one out
of the query string.