Convert classes from Mongoid to ActiveRecord
Remove mongodb from tests
Fix broken tests after conversion from Mongoid to ActiveRecord.
Add supporting code for data migration
Rename comment's content from comment body
Reimplement breakdowns
Reimplmement finding by username
Fix user#latest_submission_on
Fix remaining outstanding Mongoid to ActiveRecord tests
Fix newly created Mongo - ActiveRecord issues
Prepare code for Active Record 4
Fix conflict with cohort tests