title: zombie.js xhr json always fail
body: <p>I want to use zombie js to test my little node app.
  I'm using the mock ressoures with zombie but when i write</p>
  
  <p>body: object</p>
  
  <p>in mock.the xhr always fail because of </p>
  
  <pre><code>Request Failed: parsererror, SyntaxError: Unexpected token o
  </code></pre>
  
  <p>when i write</p>
  
  <p>body: 'json content'</p>
  
  <p>xhr work well</p>
  
  <p>To test this client js</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var xhrGetRiver = $.getJSON("api/1/settings/rivers/fs/")
  xhrGetRiver.done(function(json) {
      console.log(json);
      $.each(json, function(index, fsriver) {
          insertFSRiver(fsriver);
      });
  });
  xhrGetRiver.fail(function(jqxhr, textStatus, error) {
      var err = textStatus + ', ' + error;
      console.log("Request Failed: " + err);
  });</code></pre>
  </div>
  </div>
  </p>
  
  <p>I have write this test
  <div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var data = [];
  var json = {
    "id": "test",
    "properties": {
      "url": "/tmp",
      "server": "192.168.9.2",
      "port": 22,
      "username": "testUser",
      "password": "test",
      "protocol": "ssh",
      "update_rate": "15m",
      "includes": "*.docx"
    }
  };
  data.push(json);
  this.browser.resources.mock('/api/1/settings/rivers/fs/', {
                  statusCode: 200,
                  headers:    { 'ContentType': 'application/json' },
                  body: data  // xhr fail
                  //body: '[ { "id":... ... } ]' // Work well</code></pre>
  </div>
  </div>
  </p>