Misc renames (#202)

This patch renames a number of types and functions making
the API more consistent.

* `Server` -> `Connection`
* `Client` -> `SendRequest`
* `Respond` -> `SendResponse`.

It also moves the handshake fns off of `Connection` and make
them free fns in the module. And `Connection::builder` is removed
in favor of `Builder::new`.

examples/akamai.rs

@@ -8,7 +8,7 @@ extern crate tokio_core;
 extern crate tokio_rustls;
 extern crate webpki_roots;
 
-use h2::client::Client;
+use h2::client;
 
 use futures::*;
 use http::{Method, Request};
@@ -64,7 +64,7 @@ pub fn main() {
                 let tls = io_dump::Dump::to_stdout(tls);
 
                 println!("Starting client handshake");
-                Client::handshake(tls)
+                client::handshake(tls)
             })
             .then(|res| {
                 let (mut client, h2) = res.unwrap();