[rabbitmq] Bunny 1.1.8+

[Change log](http://blog.rubyrabbitmq.info/blog/2014/03/27/bunny-1-dot-1-8-is-released/)
Merge pull request #1208 from michaelklishin/patch-1

[rabbitmq] Bunny 1.1.8+
Merge git://github.com/logstash/logstash