This introduces the `hyper::service` module, which replaces
`tokio-service`.
Since the trait is specific to hyper, its associated
types have been adjusted. It didn't make sense to need to define
`Service<Request=http::Request>`, since we already know the context is
HTTP. Instead, the request and response bodies are associated types now,
and slightly stricter bounds have been placed on `Error`.
The helpers `service_fn` and `service_fn_ok` should be sufficient for
now to ease creating `Service`s.
The `NewService` trait now allows service creation to also be
asynchronous.
These traits are similar to `tower` in nature, and possibly will be
replaced completely by it in the future. For now, hyper defining its own
allows the traits to have better context, and prevents breaking changes
in `tower` from affecting hyper.
Closes#1461
BREAKING CHANGE: The `Service` trait has changed: it has some changed
associated types, and `call` is now bound to `&mut self`.
The `NewService` trait has changed: it has some changed associated
types, and `new_service` now returns a `Future`.
`Client` no longer implements `Service` for now.
`hyper::server::conn::Serve` now returns `Connecting` instead of
`Connection`s, since `new_service` can now return a `Future`. The
`Connecting` is a future wrapping the new service future, returning
a `Connection` afterwards. In many cases, `Future::flatten` can be
used.
