Makes user concepts work
Merge pull request #4 from LearnFast/user_concepts_work

Makes user concepts work
added the appropraite foreign keys to the models
new concepts are associtated with a user
concepts to be learned are selected based on the review date in the user_concepts
added a proper self join on the attempts table for subsequent and previous attempts
made the controller code sexier
cant seem to update model attritubes inside models public method, user_concept
save! inside method not working
added a bang to a method name