title: Select2 Dropdown Multiple select and unselect
body: <p>I have a <code>select2</code> dropdown with 4 options code is:</p>
  
  <pre><code>&lt;select id="ddlInqOn" class="InqSelect2 form-control"&gt;
    &lt;option value="1"&gt;--All--&lt;/option&gt;
    &lt;option value="2"&gt;Today Date&lt;/option&gt;
    &lt;option value="3"&gt;Past Date&lt;/option&gt;
    &lt;option value="4"&gt;Feature Date&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p><code>select2</code> called by this <code>javascript</code>:</p>
  
  <pre><code>$('.InqSelect2').select2({
    dropdownAutoWidth: 'true',
    multiple: true
  });
  </code></pre>
  
  <p>I want to achieve like when I click all option then remove other options and if other option is selected then remove all option from selection.</p>
  
  <p>I have tried this code:</p>
  
  <pre><code>$('body').on('change', '#ddlInqOn', function() {
    debugger;
    //
  });
  </code></pre>
  
  <p>but the change event is not triggred so any other possibility to track change event of select2 dropdown?</p>