http: graceful shutdown of server

[andybons]

From: https://code.google.com/p/go/issues/detail?id=4674:

Status update: Go 1.3 will have all the necessary net/http changes (Server.ConnState and
Server.SetKeepAlivesEnabled) for other people to implement graceful shutdown properly,
outside the net/http package.

Go 1.3 is out and we are compiling against it. We should shut down the servers gracefully.

Take a look at func (s *server) stop() in server/server.go

[andybons]

Also some goodness from this thread: https://groups.google.com/forum/#!topic/golang-nuts/vLHWa5sHnCE

[andybons]

https://github.com/facebookgo/httpdown and https://github.com/facebookgo/grace

[spencerkimball]

httpdown looks pretty damn good. Reminds me that I wrote the same code for GSE back in 2002.

[spencerkimball]

Closed by #636