code: function writeAndWait(data, callback) {
  	debug('write request and wait for response');
  
  	var requestId = generateGUID()
  		, envelope = {
  			plugin: 'primus-responder'
  			, requestId: requestId
  			, data: data
  		};
  
  	this.responseCallbacks[requestId] = callback;
  
  	this.write(envelope);
  }
docs: Function: writeAndWait
  Sends the passed data to the spark. As soon as PrimusResponder recieved
  a related response, `callback` is executed.
  
  Example:
  
  spark.writeAndWait('primusresponder test', function(response) {
  console.log('PrimusResponder response arrived: ' + response);
  });
  
  Parameters:
  (Object) data - Data to send along the request
  (Function) callback - Executed as soon as the response on this request
  arrived.