A teacher should be able to assign a quiz to a live class

[vansaltzman]

A teacher should have to confirm before launching
Should also have to set the time allotted for that quiz

The timer should be optional

A teacher should be able to end a quiz before the timer is over
Should see the option to return to class (will give an error if a quiz is live)

At end of a quiz:
Teachers should see:
The same view - but with some indicator that quiz is no longer active
Students should see:
Should show their results by question.
Have a button to return to class view.