====== Ajax ======
Abstraction method for XMLHttpRequest

===== Karma.ajax( options ) =====

Options
  * type: (string) can be 'GET' or 'POST', defaults to 'GET'
  * url: (string, required) the URL of the document
  * data: (string) serialized data to be passed the document, defaults to ''
  * contentType: (string) Sets the content type header.
  * loading: (function) Runs when the request has started.
  * success: (function) Runs when the request has successfully completed.
  * error: (function) Runs when the request has encountered an error.
  * XHR: (XHR object) Uses the provided XHR object instead of the default.

<code javascript>
Karma.ajax({
  type: 'POST',
  url: 'ajax.php',
  data: 'sex=male&age=12',
  success: function(o) {
    alert(o);
  }
});
</code>