code: function createResponder(source, topic, uuid) {
  		return function(message, keepalive, callback) {
  			post(source, topic, message, uuid, keepalive, callback);
  		};
  	}
docs: Helper closure to create a function that may be used to respond to a message
  @private
  @param  {Window} source The window from which the message originated
  @param  {String} topic  The topic of the message
  @param  {String} uuid   The "unique" ID of the original message
  @return {Function}      A function that may be invoked to respond to the message