playing_card: Reorganize and fix comparators.
playing_card: Reorganize and fix comparators.

Rob noticed that there were still some errors here; specifically,
there were two __gt__() implementations and no __ge__().  His pull
request couldn't apply cleanly because I had made some but not all
of the changes locally; nevertheless, this is equivalent to his
work and fixes issue #10 as well.

sunfall/giles