Decoupled StackExchangeChat and JavaBot. 

Added Interface to describe classes that 'produce' stuff and can be subscribed to. Added interface describing minimal ChatInterfacing functionality (namely queryMessages and sendMessage). see #9
There doesn't really induce any harm in letting the timeout do its job. There is a way but I'm more leaning "let's not do that just yet". For the record, a post request to `/leave-all` will do.