title: Removing AVPlayerItem observers
body: <p>If I use KVO to observe my player items like this:</p>
  
  <pre><code>    AVPlayerItem *playerItem = [AVPlayerItem playerItemWithURL:url];
      [playerItem addObserver:self forKeyPath:@"status" options:NSKeyValueObservingOptionNew context:MyClassKVOContext];
      [playerItem addObserver:self forKeyPath:@"playbackBufferEmpty" options:NSKeyValueObservingOptionNew context:MyClassKVOContext];
      [playerItem addObserver:self forKeyPath:@"playbackLikelyToKeepUp" options:NSKeyValueObservingOptionNew context:MyClassKVOContext];
      [playerItem addObserver:self forKeyPath:@"loadedTimeRanges" options:NSKeyValueObservingOptionNew context:MyClassKVOContext];
  </code></pre>
  
  <p>Two questions:</p>
  
  <p>1) Do I need to remove my observers once the item finishes playing? (i.e. in <code>AVPlayerItemDidPlayToEndTimeNotification</code>)</p>
  
  <p>2) If I call <code>[_avQueuePlayer removeAllItems]</code> does it also remove each item's observers?</p>