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.

src/proto/h1/parse.rs

@@ -132,6 +132,10 @@ impl Http1Transaction for ServerTransaction {
         extend(dst, b"\r\n");
         body
     }
+
+    fn should_error_on_parse_eof() -> bool {
+        false
+    }
 }
 
 impl ServerTransaction {
@@ -281,6 +285,10 @@ impl Http1Transaction for ClientTransaction {
 
         body
     }
+
+    fn should_error_on_parse_eof() -> bool {
+        true
+    }
 }
 
 impl ClientTransaction {