multiple instructor users

[trevorcampbell]

Currently there is only one instructor user in the rudaux config

c.instructor_user = "blah"

Should be able to specify a list of instructor jhub users for each course group. So something like

c.instructor_users = {
   'group_name_1' : ['instructor_1', 'instructor_2', 'instructor_3'],
   'group_name_2' : ['instructor_4', 'instructor_1']
}

All instructor users for a particular course group:

• get email notifications when there are grades to post
• can log into any normal grading user account (to check TA grading if needed)

Right now the above is just for one instructor, but you guys will need this to work for multiple instructors this semester.

[trevorcampbell]

@Lourenzutti after #155 do this one next!