Some fixes

Fix for Ruby1.9+ where strings are no longer bytes but characters. on_audio would crash the program.
Fix error thrown when exiting before connection is made. When the program is shut down it tries to debug on the first client but crashes if there is no client.
Update Mumble.proto and Mumble.pb.rb.
Move config.rb to config.rb.example.

Also :admin => true/false in the config.rb doesn't seem to be used.