Update benchmarks and introduce more default type params for remaining generics

The client benchmarks did not have to be changed at all for this whole
refactor, and the server benchmark only had to specify a single type parameter,
and only because it writes out the type of Listener, which is not normal
usage.

benches/client.rs

@@ -8,8 +8,9 @@ extern crate test;
 use std::fmt::{mod, Show};
 use std::io::net::ip::Ipv4Addr;
 use hyper::server::{Incoming, Server};
+use hyper::net::HttpAcceptor;
 
-fn listen() -> hyper::server::Listening {
+fn listen() -> hyper::server::Listening<HttpAcceptor> {
     let server = Server::http(Ipv4Addr(127, 0, 0, 1), 0);
     server.listen(handle).unwrap()
 }