Removed unused import
Reduced size of synch block to only include the quiz server
Changed synch
Used to be on the quiz server obj, now it's just on the method that
updates the quiz list. This way the server can work concurrently
Active games now increments if quiz is ACTIVE.
Did this by synchronising on quiz so that the status can't change in the
meantime.
removed completed comment
Added code to decrement # of active games once attempt is submitted
Added reminders re: what's required to sort attempts by score