Make it possible to rename teams

[ecridge]

For the workaround in #5 to be useful, it has to be possible to renumber teams. For instance, if there are 10 teams and number 7 drops out mid-session, you'll need to restart the session with 9 teams and use the new number 7 to represent number 10.

For the sake of a couple lines of code, it is probably worth expanding this to let teams be named as an arbitrary String, so that teams can optionally specify a (short) team name or other identifier rather than the default number.