Issues/24 and other fixes

This rolls together a number of fixes I'm working on:
* fixes #20 by adding a bunch of logging
* fixes #24 by making sure that messages are properly base64 decoded when received
* fixes another issue by converting PEM server certificates to the required DER format
* fixes an issue where Config.getboolean doesn't recognize 'yes' as a True value
* if the Listener thread gets an exception decoding the message, catch and log it. Otherwise, the python process locks up and needs to be manually killed (issue with uncaught exceptions in threads)

With all of this work, the 'simple_action.py' example now works in my environment.