add a contribute.json file (bug 1074452)

I did my best to find all the data to populate the json file, but l'm assuming I'll need to make a change or two. 
This looks unpredictable. 
It might work because you're running `./manage.py runserver` which puts the current working directory in the root of the repo. However, when you run things in mod_wsgi, gunicorn or uWsgi this is less predictable. 

I'm not very familiar with how this repo works but don't you have something like `settings.ROOT` to point to the repository? So you can use `file = os.path.join(settings.ROOT, 'contribute.json')`