title: Select2 off('change').on('change'.....) does not able to change the selected option
body: <p>I use Select2-4.0.0  And</p>
  
  <pre><code>$gameSelect.select2().on("change",function(e){....}
  </code></pre>
  
  <p>works fine. </p>
  
  <p>But when I chain it following off('change') like:</p>
  
  <pre><code>$gameSelect.select2().off('change').on("change",function(e){....}
  </code></pre>
  
  <p>The event is triggered but the selected item does not change at UI.</p>
  
  <p>Why is that?</p>