feat(lib): add support to disable tokio-proto internals

For now, this adds `client::Config::no_proto`, `server::Http::no_proto`,
and `server::Server::no_proto` to skip tokio-proto implementations, and
use an internal dispatch system instead.

`Http::no_proto` is similar to `Http::bind_connection`, but returns a
`Connection` that is a `Future` to drive HTTP with the provided service.
Any errors prior to parsing a request, and after delivering a response
(but before flush the response body) will be returned from this future.

See #1342 for more.

examples/client.rs

@@ -1,4 +1,4 @@
-#![deny(warnings)]
+//#![deny(warnings)]
 extern crate futures;
 extern crate hyper;
 extern crate tokio_core;
@@ -32,7 +32,9 @@ fn main() {
 
     let mut core = tokio_core::reactor::Core::new().unwrap();
     let handle = core.handle();
-    let client = Client::new(&handle);
+    let client = Client::configure()
+        .no_proto()
+        .build(&handle);
 
     let work = client.get(url).and_then(|res| {
         println!("Response: {}", res.status());