title: Add CSS Class with Knockout Validator
body: <p>I want to add a CSS Class to a <code>select</code> element in my view, my view model has a property which I've extended using Knockout-Validation:</p>
  
  <pre><code>self.selectedRootCause = ko.observable().extend({
      required: true
  });
  </code></pre>
  
  <p>Then my <code>select</code> is like so:</p>
  
  <pre><code>&lt;form data-bind="submit: closeComplaint" method="post"&gt; 
      &lt;select data-bind="options: rootCauses, 
                              optionsText: 'RootCauseText', 
                              value: selectedRootCause, 
                              optionsCaption: 'Choose..',
                              validationOptions: { errorElementClass: 
                                                   'input-validation-error' }"&gt;
      &lt;/select&gt;
  
      &lt;input type="submit" value="Close Complaint" /&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>My <code>closeComplaint</code> function looks like so:</p>
  
  <pre><code>self.closeComplaint = function () {
      if (self.errors().length == 0) {
          $.ajax({
              url: '@Url.Action("CloseComplaint")',
              data: new DetailsComplaintAdmin(self.currentComplaint(),
                                          self.selectedRootCause().RootCauseId
                  ),
              success: function (data) {
                  console.log(data);
              }
          });
      }
  }
  </code></pre>
  
  <p>Just for completion, here is my <code>self.errors()</code> function:</p>
  
  <pre><code>self.errors = ko.validation.group(self);
  </code></pre>
  
  <p>The problem is the class <code>input-validation-error</code> doesn't appear to be added to my <code>select</code> input when I submit my form? Any ideas?</p>