Fix bug causing sounds to play only once on Chrome

Hi,

Thanks for the convenient ion.sound library! I tried using it in a webapp today and ran into one snag under Chrome 38.0.2125.111 m on Windows 8: my sounds would only play once, then never again until the page was reloaded. Someone on StackOverflow [reported similar a problem](http://stackoverflow.com/questions/9335577/html5-audio-sound-only-plays-once) with HTML 5 sound. They fixed the problem by adding an extra .load() on the audio object before each .play(). Making a similar patch to ion.sound fixed it for me.

Regards,
-Jeremy