title: using knockout to set css class with an if condition
body: <p>I want to set a bootstrap css class to a span with if condition (up to the binded value).
  I have <code>isApproved</code> field in a list, I want to see the field with 'label-success' class when its active and 'label-important' class when its inactive</p>
  <p>I added this line, but all the time it's taking the first class</p>
  <pre><code>data-bind=&quot;
      text: isApproved,
      css: isApproved = 'true' ? 'label label-important' : 'label label-important'&quot;
  </code></pre>
  <p>Is it possible in the html or I should add a computed field on my VM?</p>