Feature/carter tests

fixed old remove_from_section tests to include resource_link_id
added four new tests to test resource_link_id match, course_id match, conclude_enrollment success and failure
views.py - cleaned unnecessary exception checking from remove_from_section to put it in line with similar functions
removed some unused includes
I saw another pair of almost similar methods further down  and noticed that they differ slightly in terms of one testing render and another the status. Probably a more detailed  description would help.. Skip the removal .