removes separator argument to Time.fromUnitString in ChallengeGraph - value passed is now the default
changes Lightsquare to only navigate to the game rematch if the user is on the game

this prevents rematches hijacking the focus if the user is playing another game at
the same time
adds startUpdating to RandomGames and removes send(/random_games...) from getGames -
to refresh the list and start updating, code must call startUpdating as well as
getGames().then(...).

the getGames promise can be obtained at any time, but it won't be resolved until
something calls startUpdating and the server replies with /random_games.
adds CurrentGames widget module.  the template still needs writing - the plan
is to implement the boards entirely with Ractive templates so that no tedious
update logic has to be written.
adds CurrentGames widget (not finished) to the home tab on the HomePage