v0.5.0

• Core functions have been rewrited
• Now supporting shuffle songs, to enable shuffle mode, via player.enable('shuffle') or parse a option.shuffle = true when initing player instance.
• API added:
  • player.enable() enable a option after instance inited
  • player.disable() disable a option after instance inited
  • getter list via this.list
  • getter playing via this.playing
• API changed:
  • player.play() DO NOT accept callback function anymore, to add a listener to play done, use player.on('finish') instead.
  • player.next() DO NOT accept callback function anymore.