add hangouts! handler

@mdimas @vijaykramesh @erikogan @mrubens @orfah 

How does this look for a first-pass at a simple lita handler to create a new google hangout link on-demand?

I have it running in staging mode in the "Lita" chat room right now.

I made it so you have to write "hangouts!" (with the exclamation point) to create a new google hangout and each new room is simply created with a UTC timestamp.
It might be nice to use the name of the room in the hangout, but I'm not sure how much more difficult that would be.