Add README.md with bug report

src/main.rs

@@ -1,8 +1,7 @@
 use std::convert::Infallible;
-use std::future::Future;
 use std::net::SocketAddr;
 
-use futures::{future, FutureExt};
+use futures::future;
 use hyper::service::make_service_fn;
 use warp::Filter;
 
@@ -10,6 +9,8 @@ fn main() {
     let svc = warp::service(
         warp::path::end()
             .map(|| "Hello, world")
+            // Try commenting out this line to make the program compile again.
+            // vvvvvvvvvvvvvvvvvvvvvvvvvvv
             .with(warp::trace::request()),
     );
     let make_svc = make_service_fn(move |_| future::ok::<_, Infallible>(svc.clone()));