* grey dice which are not clickable, and make disabled dice unclickable even if it's your turn
* when initializing Api, initialize active_games and completed_games too
* also initialize button and player
* try to improve code cleanliness of Api module by implementing it
  as an anonymous function
* small fixes to make jshint happier
* improve test coverage of Api.js and remove a bit of obsolete logic
  from before active games and completed games were split
* GAME_STATE_END_GAME is no longer needed in Api.js, because responder
  tells us which games are completed
Merge pull request #454 from cgolubi1/430_dizzy_ui

make "disabled" dice unclickable, and put unclickable dice on a grey background