Refine referee tests.

These are new tests to make the referee more robust.  Most of these
enhancements are based on watching various students implement the
referee incorrectly while passing all the existing tests.  These new
tests will make it harder for that to occur.
Create new tests for contest model

These tests are the beginning to ensure the contests are created
properly.  There are more functionality tests needed (e.g., ensure two
contests with the same name cannot be added), but the basics are in
place now.  This will provide a nice basis to ensure the contests are
written properly.
Merge branch 'master' of https://github.com/geisler/game_contest_server into dev
Merge branch 'master' of https://github.com/geisler/game_contest_server into dev
Passing all new tests