Fours! inspired by 2048

Inspired by the game 2048: http://gabrielecirulli.github.io/2048

New rules are introduced in the game. Swipe with your finger to move numbers between tiles. '1' and '3' merge into '4'. Two tiles with the same number greater than or equal to 4 merge into one. The goal in the game is to get to 1024 tile.