Cleanly exit on SIGINT

[colindean]

As best I can tell, the program just exists when Ctrl+C interrupted. Can we make it part nicely?

[colindean]

[4:46pm] rhettigan: cl0ckw0rk: looks like cinch itself doesn't have a method which cleanly exits
[4:49pm] rhettigan: Cinch::IRC#start_reading_thread handles disconnection and timeout and cleans up by closing the socket and dispatching :disconnect to all of the handlers
[4:50pm] rhettigan: I think Cinch just needs to handle Interrupt in the rescue for the read loop
[4:50pm] rhettigan: https://github.com/cinchrb/cinch/blob/master/lib/cinch/irc.rb#L146