title: knockout "observable is not a function" when declaring a datepicker
body: <p>In the html I have this <code>select</code>:</p>
  
  <pre><code>&lt;input class="form-control input-sm" data-bind="datepicker: StartDate" /&gt;
  </code></pre>
  
  <p>It's not inside of a loop.  Just a standalone.  And inside the knockout model, I am trying to define it as follows:</p>
  
  <pre><code>function VacationRequestsViewModel() {
      var self = this;
      self.StartDate = new Date();
      ....
  }
  </code></pre>
  
  <p>And this too....</p>
  
  <pre><code>$(document).on('ready',
      function () {
          masterVM = new VacationRequestsViewModel();
          ko.applyBindings(masterVM);
      });
  </code></pre>
  
  <p>On page load, I get this</p>
  
  <blockquote>
    <p>Uncaught TypeError: Unable to process binding "datepicker: function (){return StartDate }"
    Message: observable is not a function</p>
  </blockquote>
  
  <p>I have successfully declared lots of other things.  Observable's.  ObservableArray's   Bool's.  Not sure what I'm doing wrong here.</p>