Add congratulations modal and toasters

[lbkchen]

• Congrats modal should appear at the end of a course (add a graphic or something to make it fun) when a student completes the last component. Should also contain a redirect back to the all courses page. Also, indicate that the student can now see all courses offered and also request for more courses
• Make sure the requestable courses is the correct subset of courses (published but not enrolled already)
• Add toasters for various user actions (see Charles's example for adding courses with codes). Some places I can think of right now that need them (and use your best judgment to think of more):
  • Approving/rejecting a student course request (admin)
  • Updating your profile successfully
  • Students requesting courses
  • Admin publish/unpublishing a course
  • Admin generating codes
  • Admin importing a course