Adds projects_url attribute to course resource
Updates empty responses in course resource to have status code 204
Changes user_id field to plain old id in api documentation
Merge remote-tracking branch 'remotes/origin/api'

* remotes/origin/api:
  Changes user_id field to plain old id in api documentation
  Updates empty responses in course resource to have status code 204
  Adds projects_url attribute to course resource