* More tests for mongo modulestore, including tweaks to test files
* add location_to_id method to CourseDescriptors
* Implement path_to_location method in mongo.py
- TODO: does not handle position in sequences yet.
* fix bug in jump_to view.
* Clean up test data for simple, toy courses
* clean up test_mongo.py
* write initial test for path_to_location
* hook up view to use path_to_location
Next: actually implement it :)