code: function xhrJson(method, url, options) {
  		if (options && typeof options.data !== 'undefined') {
  			options.data = JSON.stringify(options.data);
  		}
  		return xhr.apply(null, Array.prototype.slice.call(arguments)).then(function(result) {
  			return JSON.parse(result.response || null);
  		});
  	}
docs: Invoke the xhr API passing JSON data and returning the response as JSON.
  @returns {Deferred} A deferred that resolves to a JS object, or null if the server returned
  an empty response.