[Request] Add support for starting and stopping the server easily

[frakman1]

I'm trying to integrate Droopy in some of my code but it's hard to use because there is no way to stop the server reliably. I've implemented something that starts Droopy in a new thread and even stops it but I can't then start it up again. I had to override the serve_forever function with some code like this

A simple, externally available start and stop routine would be nice.