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
Fix bug in current user logic
Make db connection configurable
Move DB connection manager into db dir

I also renamed it since it seems to represent an actual connection.
Simplify user data model

* Remove 3 fields that seem accidental transfers from comment
* Use traditional timestamps instead of the :j_at
Delete whitespace
Tell Travis to migrate the database
Do not start MongoDB on Travis
Give Travis a directory to put the database in