Update CoinFlip3D.java

I added the sound code for the game. The game now has the following:
- A coin sound effect when the player hits the space bar key.
- An ambient sound looped through the game play duration.

Summary of updates:
- Declared natureAudio and coinFlipAudio AudioNode objects
- Created an initAudio() function
- Added the initAudio(); statement inside LoadMainGame() function
- Added the coinFlipAudio.playInstance(); statement inside the flipCoin() function
- Added the natureAudio.play(); statement inside the SimpleUpdate() function

The assets location and names are:
Assets/Sounds/Effect/coinToss.wav
Assets/Sounds/Environment/outdoors.ogg