Added extra buttons:

- Implemented retry button*
- Escape on mode select sends you to title screen
- Escape on title screen closes the game
- Added "Exit Game" entry on title screen, closes the game when selected

*Pardon my angry comment in `scene/game.lua`.

tetris/modes/gamemode.lua

@@ -68,6 +68,7 @@ end
 
 function GameMode:initialize(ruleset)
 	-- generate next queue
+    self:new()
 	for i = 1, self.next_queue_length do
 		table.insert(self.next_queue, self:getNextPiece(ruleset))
 	end