Add support for sending messages to a specified room/flow

This would fix https://github.com/flowdock/hubot-flowdock/issues/31

It allows scripts to send messages to a flow by name such as `main`. Names are lowercased which should be fine since Flowdock doesn't allow flows to be created with the same case-insensitive name.

I tried to keep the code formatting consistent, I won't be offended if you fix it up though.



P.S. i.TV <3 Flowdock