MediaPlayerHolder
Author: @Jeluchu
This class is used to play music with MediaPlayer
Once the MediaPlayer is released, it can't be used again, and another one has to be created. In the onStop() method of the Activity the MediaPlayer is released. Then in the onStart() of the Activity a new MediaPlayer object has to be created. That's why this method is private, and called by load(int) and not the constructor.
References PlayerAdapter and PlaybackInfoListener