Use SM2 multiple formats url feature

Thank you for the great component, does its job really well.

I was trying to specify the url parameter in multiple formats as mentioned in
http://www.schillmania.com/projects/soundmanager2/doc/#smsound-url and unfortunately failed to do that.

My first guess was updating the propTypes in the source code. So on the line 246 instead of

  url: _propTypes2.default.string.isRequired,

I put

  url: _propTypes2.default.oneOfType([
    _propTypes2.default.string,
    _propTypes2.default.array
  ]).isRequired,

The test showed that the code, in fact, does not seem to cope with the multiple formats. I was trying ogg and wav like so <Sound url={["blah01.ogg", "blah01.wav"]} /> and it worked for the first file in the array. Then I renamed the first file on the server and the second wasn't loaded.

Could you please help me making it work.

Start at the source code around line 246, where Sound's url propTypes are declared, and trace how the url value is consumed. Verify the documented multiple-format URL behavior with the ["blah01.ogg", "blah01.wav"] example, including loading the second source when the first is unavailable.