Now playing notes on all channels (yes!!)

* playNotes now looks through each channel as it looks at each note, playing any notes that are turned on
* Moving note highlighting out to a separate function (though currently not working)
Fixing channel assignment so note highlighting works

* When channel switching, channel was getting assigned as a string instead of int, so when noteHighlight was going to get called, it was doing an int to string comparison instead of int to int.
Merge pull request #26 from artfoundry/play-multiple-channels

Play multiple channels