title: Knockout validation with select binding not add ErrorElement.css
body: <p>I am working with knockout and want user to choose one of item in html select tag.
  By default selected empty value</p>
  
  <pre><code>&lt;select required&gt;
              &lt;option value=""&gt;--Select something&lt;/option&gt;
              &lt;option value="True"&gt;True&lt;/option&gt;
              &lt;option value="False"&gt;False&lt;/option&gt;
  </code></pre>
  
  <p></p>
  
  <p>And viewModel contain:</p>
  
  <pre><code>self.sampleBooleanValue.extend({required : true});
  </code></pre>
  
  <p>I expected that following binding will help</p>
  
  <pre><code>&lt;select data-bind="value: sampleBooleanValue" required&gt;
  
   ....
  &lt;/select&gt;
  </code></pre>
  
  <p>Validation works, but no css class is added to select tag. 
  Can anybody tell why this not work?
  P.S. It works with another inputs tags.</p>