Moved from simplejson to json module
Requirements update

- Django 1.6
- Celery 3.1

Use the celery command directly for running celery-related tasks from now on! See the documentation for examples.
Celery 3.1 Async Worker Update

Allows us to perform Celery tasks asynchronously via Eventlet's green threads.

- Update from Celery 3.0 to Celery 3.1
- JSON is the default serializer now
- Task results will expire after 5 minutes
- See the 'installation' docs for further details
Removed unnecessary Celery serializers