Revert "refactor(lib): convert to futures 0.2.0-beta (#1470)"

This reverts commit a12f7beed9.

Much sadness 😢.

src/lib.rs

@@ -18,6 +18,7 @@
 
 extern crate bytes;
 #[macro_use] extern crate futures;
+extern crate futures_cpupool;
 extern crate futures_timer;
 extern crate http;
 extern crate httparse;
@@ -27,6 +28,8 @@ extern crate net2;
 extern crate time;
 extern crate tokio;
 extern crate tokio_executor;
+#[macro_use] extern crate tokio_io;
+extern crate tokio_service;
 extern crate want;
 
 #[cfg(all(test, feature = "nightly"))]
@@ -46,8 +49,7 @@ pub use error::{Result, Error};
 pub use proto::{body, Body, Chunk};
 pub use server::Server;
 
-mod executor;
-mod service;
+mod common;
 #[cfg(test)]
 mod mock;
 pub mod client;