Add the stats queue to the celery invoking command
Bugfix in the stats handler for answer updating
Now superusers can view the courses even if they expired.
Added code documentation following the guidelines
Fixed minor typo in a javascript tag
Create the stats docs when creating the models

Using post save signals, create or update the stats document in the
mongo db after saving changes in the model instances
Added documentation to courses administration
Added minor documentation reference to course backend
Added minor reference documentation to course announcement feed
Added partial documentation to course mark system
Removed old code that now it's in marks.py
Added code documentation to security validations
Added code documentation to course utils and widgets
Added code documentation for some parts of teacheradmin
Command to generate a csv with the students stats
Add dates to the generated csv with the extra students stats
Prevent multiple clicking in the form and disable button
Refactored Javascript code for mass emailing
Make send_in_batches a task so the form can answer quickly to the mass mailing command