Added callback to play method

[otari]

i have added possibility to path callback method in ion.sound.play() method which is triggered if this.file_not_found flag is set to true during fetching data from server. and it only works if you set preload:true during plugin initialization.

example usage:

$('.trigger').on('click',function(e) {
     ion.sound.play("bell_ringoo", {
          callback:function(result) {
               console.log(result);
         }
    });
});