Added sounds

the sound manager can be accessed through game.sound. The three methods that you should be using are:
1) game.sound.add(key), which adds the sound
2) game.sound.play(key), which plays the sound
3) game.sound.stopAll(), which stops all of the sounds
Merge branch 'master' of https://github.com/Maplenormandy/plunderwinds

Conflicts:
	game/states/play.js
Merge branch 'master' of https://github.com/Maplenormandy/plunderwinds
added credits and changed tiles

please do not remove the game from index.html because that's where the music attributions are :(
also made the bottom right square more clear that it is the gold.