docs(readme): add Greenkeeper badge

Author: greenkeeper[bot]

README.md

@@ -1,4 +1,6 @@
 # loopback-component-mq
+
+[![Greenkeeper badge](https://badges.greenkeeper.io/fullcube/loopback-component-mq.svg)](https://greenkeeper.io/)
 Loopback Component for working with a Rabbit Message Queue.
 
 [![Circle CI](https://circleci.com/gh/fullcube/loopback-component-mq.svg?style=svg)](https://circleci.com/gh/fullcube/loopback-component-mq) [![Dependencies](http://img.shields.io/david/fullcube/loopback-component-mq.svg?style=flat)](https://david-dm.org/fullcube/loopback-component-mq) [![Coverage Status](https://coveralls.io/repos/github/fullcube/loopback-component-mq/badge.svg?branch=master)](https://coveralls.io/github/fullcube/loopback-component-mq?branch=master)