[bug 1089650] Add a contribute.json file

Instead of asking all the usual questions like "Where is the code?",
"Where is the staging server?", "Do we have a mailing list?" you can
simply look all this up in the /contribute.json file.
[bug 1089650] Add test to verify that the JSON is valid

A test now checks if contribute.json is valid JSON.
Merge new code from master
Merge pull request #373 from bkowshik/master

[bug 1089650] Add a contribute.json file
Add Bhargav Kowshik to CONTRIBUTORS
Fix throttle test

This fixes the throttle test so that it clears the cache before running
the test and also pauses between HTTP requests. This reduces the
likelihood that it bumps into submitted responses from other tests. The
slight pause makes it pass consistently on my local machine.

Added a FIXME to look into the "pause" thing further because that's
total goofipants.
[bug 1072285] Update Django, django-nose and django-cache-machine

* update Django to 1.6.8
* update django-nose to latest in master because they don't like doing
  releases (b81f847)
* update django-cache-machine to latest in master because they don't
  like doing releases (f827f05)
[bug 1072285] Update django-adminplus

v0.3 of django-adminplus has fixes in it for Django 1.6, so this is
required.
[bug 1072285] Update requirements.txt file