[rabbitmq] Use Bunny 0.9.1+
[rabbitmq] Use Bunny 0.9.1+

Nothing major in `0.9.1` but I'd like Logstash to keep up with recent releases.
Aloomaio/logstash-kafka,opentable/logstash-kafka,joekiller/logstash-kafka,tinglinux/logstash-kafka,opentable/logstash-kafka,joekiller/logstash-kafka,tinglinux/logstash-kafka,Aloomaio/logstash-kafka