Removing celery role from ansible playbooks

Turns out we aren't using supervisor anymore but rather the upstart
scripts. All the celery role did was provide supervisor scripts to run
celery. Done and done.
Set up and configure django celery + redis for git checking

We now use celery and redis to manage periodic checking of repositories
for git commits. This should be a little more flexible than using cron
jobs and you can also monitor the tasks health as well.
Adds celery upstart files to ansible deployment

We need celery and celerybeat to be running on our box. The other thing
that we ought to enable in our next commit is setting up JUST a celery
box, where the broker variable gets set to the primary web server. That
would enable spinning up multipe task queue servers.
Merge branch 'feature/celery-task-management' into develop

* feature/celery-task-management:
  Adds celery upstart files to ansible deployment
  Set up and configure django celery + redis for git checking
  Removing celery role from ansible playbooks