title: get selected option text in knockout
body: <p>I am using knockoutjs to bind a select list. Here is a <a href="http://jsfiddle.net/LHjBq/">Sample</a>
  , I want to get selected option text instead of selected value.</p>
  
  <p>How to get it using knockoutjs ?</p>
  
  <pre><code>&lt;select id="projectMenu" name="projectMenu" data-bind="   
          value: selectedProject,
          options:        projectFilters,
          optionsText:    'a', 
          optionsValue:   'b',   
          optionsCaption: '-- Select Project --'
      "&gt;
      &lt;/select&gt;
  &lt;b&gt;Selected Project:&lt;/b&gt; &lt;span data-bind="text: selectedProject"&gt;&lt;/span&gt;
  </code></pre>