Add sounds to the game

[ivstefano]

Currently there is a sounds folder in the webroot.
Adding them to the game would be nice, since it would make it more lovable.

1. Ambient background
2. Pirate 'Rrrr'-ing when Start button is clicked
3. Coin cha-ching sound when collected
4. Multiple 'Rrrr' sounds when 5 coins are collected
5. Multi-voice 'Rrrr' when all of the coins are collected.