Minor cleanup based on @ismith's feedback
Update the READMe with the latest changes to support JMS
Force Stapfen::Client::Stomp to deep-copy the configuration as a workaround to <https://github.com/stompgem/stomp/issues/80>
Add a CHANGES document to start keeping track of user-facing changes between versions
Add #closed? to the Stapfen::Client API to make the worker code a bit cleaner
Make sure that evaluation of the log block happens in the instance instead of class

Fixes #3