command/playbackstate fixes

v0.13 - 2016-05-01 - owagner

• change logic for command/playbackstate:
  • resume/play/1 will now properly resume when pausing, and attempt to
    start play when playback has endeded. Fixes #17
  • pause/2 will now only pause if the player is actually playing.
    It can no longer be used to toggle pause mode.
  • toggle (new) will now toggle pause mode, similarily to how "pause"
    did before