Gracefully quit on Ctrl+C

Catch Ctrl+C, disallow new connections, kick all existing connections
and end the process with a beautiful backflip. Much better than the
"program crashed so complain to the developer" message I got until now!
Extract port number to config file

In the meantime I realised you don't need to include the file extension
when requiring JS and JSON: cool!
Pick a slightly more creative port number

The one I used is used by too many node examples already and is
apparently reserved by some DNS service.