Fix encoding, more interop and update nightly version

tower-h2/examples/client.rs

@@ -1,5 +1,3 @@
-#![feature(async_await)]
-
 use http::Request;
 use std::pin::Pin;
 use std::task::{Context, Poll};

tower-h2/examples/server.rs

@@ -1,5 +1,3 @@
-#![feature(async_await)]
-
 use futures_util::future;
 use http::{Request, Response};
 use std::pin::Pin;