As described in issue #16, commands are now processed in two stages.
First, all plugins get to give a confidence with which they are the
right plugin to handle the command. Then, the one with the highest
confidence gets to run first, and if for some reason it can't handle the
command, other plugins try in turn.
Now you can control media players supporting MPRIS using Kaylee. Just
load the plugin and commands like "play the music", "pause the video",
"previous song", and "next video" magically work.