add course_id to all emitted events

The goal here is to make a best effort attempt to include the course_id in the event.  This method will catch the vast majority of events that we emit, however, I wouldn't be surprised if some events are emitted that we want to be associated with a course but won't be using this method.

Note this adds a dependency on event-tracking.

Reviewers: @rocha, @e0d, @jtauber