title: Problems with mocking jsonp requests using mockjax in qunit
body: <p>I'd like to use mockjax with qunit but can't get it to work.
  Here is a simple test I tried: <a href="http://jsfiddle.net/shapeshifta/3YNB2/" rel="nofollow">http://jsfiddle.net/shapeshifta/3YNB2/</a></p>
  
  <pre><code>asyncTest('Response returns jsonp', function() {
      $.mockjax({
          url: 'http://search.twitter.com/search.json*',
          contentType: 'text/json',
          proxy: 'mocks/twitter.json'
      });
      window.abcdef123456 = function() {
          start();
          ok(true, 'JSONP Callback executed');
      };
  
      $.ajax({
          url: 'http://search.twitter.com/search.json?q=Javascript&amp;callback=?',
          jsonpCallback: 'abcdef123456',
          dataType: 'jsonp',
          error: function() {},
          complete: function() {}
      });
      $.mockjaxClear();
  });
  </code></pre>
  
  <p>Works like a charm without the mockjax code but does not really work with it... Am I doing soemthing wrong? Tried to use sinon.js but it has some issues with asynchronous test so I wanted to switch to mockjax. But my code just keeps asking twitter for data although mockjax should mock my request...</p>
  
  <p>Any ideas?</p>