title: Removing all notification observer from a single place
body: <p>I want to remove a notification observer and I am using the method: </p>
  
  <pre><code>[[NSNotificationCenter defaultCenter] removeObserver: name:@"myNotification" object:nil];
  </code></pre>
  
  <p>for this. Now there are many observers who are listening to this notification and I want to remove all of them in one shot from a centralised place. Can I pass 'nil' in first parameter and it will remove all observers who are listening to myNotification? </p>