feat(server): change NewService to MakeService with connection context

This adjusts the way `Service`s are created for a `hyper::Server`. The
`MakeService` trait allows receiving an argument when creating a
`Service`. The implementation for `hyper::Server` expects to pass a
reference to the accepted transport (so, `&Incoming::Item`). The user
can inspect the transport before making a `Service`.

In practice, this allows for things like getting the remote socket
address, or the TLS certification, or similar.

To prevent a breaking change, there is a blanket implementation of
`MakeService` for any `NewService`. Besides implementing `MakeService`
directly, there is also added `hyper::service::make_service_fn`.

Closes #1650

src/server/shutdown.rs

@@ -4,8 +4,8 @@ use tokio_io::{AsyncRead, AsyncWrite};
 use body::{Body, Payload};
 use common::drain::{self, Draining, Signal, Watch, Watching};
 use common::exec::{H2Exec, NewSvcExec};
-use service::{Service, NewService};
-use super::conn::{SpawnAll, UpgradeableConnection, Watcher};
+use service::Service;
+use super::conn::{MakeServiceRef, SpawnAll, UpgradeableConnection, Watcher};
 
 #[allow(missing_debug_implementations)]
 pub struct Graceful<I, S, F, E> {
@@ -40,7 +40,7 @@ where
     I: Stream,
     I::Error: Into<Box<::std::error::Error + Send + Sync>>,
     I::Item: AsyncRead + AsyncWrite + Send + 'static,
-    S: NewService<ReqBody=Body, ResBody=B>,
+    S: MakeServiceRef<I::Item, ReqBody=Body, ResBody=B>,
     S::Service: 'static,
     S::Error: Into<Box<::std::error::Error + Send + Sync>>,
     B: Payload,