Supply Bro "connection alive" and "connection delete" mechanisms.

The ability to write a disconnected broccoli client that can disconnect and reconnect as needed was missing from the python implementation.  These are 2 additional methods (connAlive and connDelete) in the Connection class.

I didn't see a great place to document these methods in README, but feel free to add as you will, or suggest a good place for me to do so.

Thanks!