work in progress commit, setting up routes, controller, and tests for feedback
Created model, controller, route for feedback.

TDD for feedback create and index route.  Index provides all feedback for a given
submission.  If no submission id is provided no feedback is returned.  Create allows
teachers to create feedback for a given submission.  Feedback can only be created by logged in teachers.
Again no feedback is created without a submission id.
Merge pull request #26 from whoisglover/feedback_routes

Feedback routes