code: function respondable(win, topic, message, keepalive, callback) {
  		var id = uuid.v1();
  		post(win, topic, message, id, keepalive, callback);
  	}
docs: Post a message to a window who may or may not respond to it.
  @param  {Window}   win      The window to post the message to
  @param  {String}   topic    The topic of the message
  @param  {Object}   message  The message content
  @param  {Boolean}  keepalive Whether to allow multiple responses - default is false
  @param  {Function} callback The function to invoke when/if the message is responded to