Add Playlist Assist.app version 1.2.1

[Playlist Assist](http://dougscripts.com/apps/playlistassistapp.php) is a floating window to which tracks from iTunes can be dragged and then sorted, arranged, auditioned, edited, exported as text, and saved back to iTunes as a new playlist.
Easy trick, here. Instead of the complicated regex, use simply `#{version.to_i}`.