Frontend: Allow songs to be dragged in

[earboxer]

I really love the interface, great for filling a screen so that multiple musicians can see it. It would be nice if we could "drop" in our own text files, (not upload, just locally view it).

[earboxer]

This can be (slightly) implemented by defining ondrop and ondragover on #songContainer

<div id="songContainer" ondrop="event.preventDefault();
  var file = event.dataTransfer.files[0];
  var reader = new FileReader();
  reader.onload = function(e){
    var text = e.target.result;
    document.getElementById('song').innerHTML = 
        '<div class=chordLyricLine>'+text+'</div>';
  }
  reader.readAsText(file);"
  ondragover="event.preventDefault();">

(of course, we wouldn't want to define it as inline javascript), and would probably want transposing to work...