Updating the documentation in accordance with Michael Klishin's remark
to Marc Limotte on 2013-06-17 on the clojure-rabbitmq list.

langohr.consumers/subscribe does not block, so the use of a short-lived Thread instance in the documentation isn't necessary.
Merge pull request #2 from malcolmsparks/master

Updating the documentation in accordance with Michael Klishin's remark