fixed merge issue for edit roster not displaying students on edit page
added the ability to delete a student's assignment from a class
added ability to edit a student's grade on for a particular assignment
added ability to update student assignment grades
added the appropriate gems and folders for rspec, added 3 passing tests for user and course associations
added enrollment and student factories as well as course tests
added group and pod factories and tests to both course and student spec
added user test for for successful login
Merge pull request #28 from zrivest/unit_testing_models_and_migrations

Unit testing models and migrations