CYB-216 Student activity before using DC app should still create student

* If a canvas_user_id appears in the stream and does not have a Student record, one is created from data retrieved with a Canvas API call
* API key for the app will have to have account level permissions; the /profile call will require a higher permission than just 'Teacher'.
Merge pull request #109 from coyote/keep_student_list_updated

CYB-216 Student activity before using DC app should still create student