Reduce lifetime requirements of `serve`.

Currently the NewService trait, and a lot of the other parameters for serve require a 'static lifetime.
I'm a bit of a Rust rookie, but wouldn't it be better to tie it to the server itself?

As it stands, there's no safe way to do something like:
(Where self is some managed state)

fn start(self, port: u16) {
	let addr = ([127, 0, 0, 1], port).into();

	let service_factory =
		|| service_fn(|req| handle_incoming(&self, req));

	let server = Server::bind(&addr)
		.serve(service_factory)
		.map_err(|e| eprintln!("Server error: {}", e));

	hyper::rt::run(server);
}

I can't take a reference to self, because the lifetime is static.
Even though, the server is started on the next line, and it blocks.
So, once it gets to the end of this method, the server would have already stopped.

Start by reading the NewService trait and the serve entry point to map where the 'static lifetime requirements are imposed. Determine whether the requested server-tied lifetimes can be supported safely, and document the affected API behavior and tests needed to demonstrate that non-static managed state works.