title: Stop audio playing when another app's audio comes in
body: <p>I would like to know how do I implement the behaviour, so that my radio streaming would stop playing if other audio would come in to play - for instance, user starts playing music, makes a call etc.</p>
  
  <p>In other words, how does my ExoPlayers knows that other audio is being played, or if it doesn't, do I have to listen for mediaplayer and call events?</p>