Update sound file paths

[lawrencexia]

In the adding flair section of the tutorial, the sound file path on the webpage is prepended with "Sound", i.e. runAction(SKAction.repeatActionForever(SKAction.playSoundFileNamed("Sounds/theme.mp3", waitForCompletion: true)))

This causes a Resource X can not be loaded error for me (Xcode v 7.3.1, Swift version 2.2). Sound file paths should just be the name of the file, such as theme.mp3, which is correct in this gh repo but not reflected in the web tutorial.

[dpaola2]

@barnes7td

[nojvek]

Thanks for this. It drove me crazy why it wasn't working.

[getaaron]

@joelip ^^^