This feature can be used in place of the pile of hacks in middleware.go,
and doesn't involve awkwardly shimming out a http.ResponseWriter. Sounds
like a win-win!

graceful.Server was made private in 05c2ca7e, but I think the increased
flexibility you get with being able to provide your own TLS options
(etc.) outweighs the API complexity of an additional type.

Apparently stdlib support will be in Go 1.3. Yay!

Package graceful provides graceful shutdown support for net/http servers,
net.Listeners and net.Conns. It does this through terrible, terrible hacks, but
"oh well!"