Plug heartbeat sender leak in clean_up_on_shutdown
Merge pull request #199 from m-o-e/fix-threading

Plug heartbeat sender leak in clean_up_on_shutdown
Update change log
Ruby version specification: use a plain .ruby-version specification

This means both RVM and rbenv will use ruby 2.0.0-p451. In addition, RVM will use the gemset called "rabbitmq".