title: <input> with readonly Attribute wont open widget
body: <p>I am trying to use the <a href="https://github.com/Eonasdan/bootstrap-datetimepicker" rel="nofollow noreferrer">https://github.com/Eonasdan/bootstrap-datetimepicker</a>
  and trying to make the input field read-only then even the date picker button getting disabled and I am not able to open the date picker widget</p>
  
  <pre><code>&lt;div class="container"&gt;
      &lt;div class="row"&gt;
          &lt;div class='col-sm-6'&gt;
              &lt;div class="form-group"&gt;
                  &lt;div class='input-group date' id='datetimepicker1'&gt;
                      &lt;input type='text' class="form-control readonly" /&gt;
                      &lt;span class="input-group-addon"&gt;
                          &lt;span class="glyphicon glyphicon-calendar"&gt;&lt;/span&gt;
                      &lt;/span&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          &lt;/div&gt;
          &lt;script type="text/javascript"&gt;
              $(function () {
                  $('#datetimepicker1').datetimepicker();
              });
          &lt;/script&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Is there any way I can make the field read-only  and still access the date pciker widget?</p>