title: Backbone fetch() send text/html request type instead of json
body: <p>I'm using YiiBackboneBoilerplate. I want to populate a model with data like this:</p>
  
  <p><strong>--model--</strong></p>
  
  <pre><code>define([
      'jquery', 
      'underscore', 
      'backbone'
      ], function($, _, Backbone) {
  
          var EvaluateModel = Backbone.Model.extend({
  
              urlRoot: 'evaluate/process',
              defaults: {
                  title: '',
                  state: 1
              }
          });
  
          return EvaluateModel;
      });
  </code></pre>
  
  <p><strong>--in my view--</strong></p>
  
  <pre><code>    initialize:function() {
          var result = new Evaluate({id:this.id});
          result.fetch({
              success: function(result, response) {
                  JSON.stringify(result.model);
              }
          });
      },
  </code></pre>
  
  <p><strong>-- Yii action --</strong></p>
  
  <pre><code>public function actionProcess() {
      //I have tryed this
      echo json_encode('test');
      Yii::app()-&gt;end();
  
      //and this
      $this-&gt;sendResponse(200, CJSON::encode(array('title' =&gt; 'test')));
  }
  </code></pre>
  
  <p>and i'm getting textStatus: parsererror and the result returned from the server contains html of the current page</p>
  
  <p>Besides, the fetch() should send a POST request type according to initial setting in the app.js, but the type is 
  GET</p>
  
  <p><strong>--app.js--</strong></p>
  
  <pre><code>// initialize Http object to make backbone work with POST instead of GET
  Http.initialize({type:'POST'});
  </code></pre>
  
  <p>What could be wrong?</p>