Complete courses from Udacity in XBMC
From http://udacity.com/how-it-works: "Udacity is the future of online higher education. (It) offer accessible, affordable, engaging classes that anyone can take, anytime."
- Updated Course Catalog to use api instead of page scraping
- Sort Course Catalog
- Sort My Courses
- Fixed bug causing plugin to fail when there's no answer video after quiz
- Separate tests into Unit and Integration tests
- Removed code supporting filtering courses by difficulty