title: Update not working with Kendo datasource
body: <p>I have an issue with Kendo Datasource, the update is never fired while the change is well fired with modified Object.</p>
  
  <p>The datasource is very simple :</p>
  
  <pre><code>    collection: new kendo.data.DataSource({
          autoSync: false,
          batch: true,
          transport: {
              read: {
                  url: "http://localhost:81/GPL/Main/Sources/GPL.Web.MVC/Vignette/Vignettes_Read",
                  dataType: "json" //"jsonp" is required for cross-domain requests; use "json" for same-domain requests
              },
              update: {
                  url: "http://localhost:81/GPL/Main/Sources/GPL.Web.MVC/Vignette/Vignette_Update",
                  dataType: "json" //"jsonp" is required for cross-domain requests; use "json" for same-domain requests
              },
              schema: {
                  model: {
                      id: "Id"
                  }
              }
          },
          change: function (e) {
  
              console.log(this);
              console.log(e);
  
              //Not working too
              //if (e.action == "itemchange") {
              //    debugger;
              //    vignettesViewModel.collection.pushUpdate(e.items[0]);
              //}
  
              $('.vignette').detach();
              for (var i = 0; i &lt; vignettesViewModel.collection.data().length; i++) { 
                  vignettesViewModel.createVignetteUI(vignettesViewModel.collection.data()[i]);                    
              }
  
              vignettesViewModel.init()
          }
      })
  </code></pre>
  
  <p>For the test, autosync is set at false and batch is set at true.</p>
  
  <p>Later in code, I update the datasource and I fired explicity the datasource by sync() methods</p>
  
  <pre><code>    //Some logic up
          var data_hospit = vignettesViewModel.getByUid($(ui.element).data('uid'));
      //Another logic
          data_hospit.set('date_debut', cellDepart.data('date'));
          data_hospit.set('date_fin', cellArrivee.data('date'));
          data_hospit.set('PrenomNomEtDateDeNaissance', 'toto');
  
          vignettesViewModel.collection.sync();
  </code></pre>
  
  <p>update is not fired but I see well that object changed go through change function.
  So why update is never fired ? 
  I have well define model with id : 'Id' and if I change update string to a dummy function alert(), this is not working too.
  I ve tried to "force" update with pushUpdate but I have got an error "undefined function"</p>
  
  <p>Thanks for your help</p>