Bump tokio-async-await to 0.1.6 (#921)

tokio-async-await/examples/src/chat.rs

@@ -61,7 +61,7 @@ async fn process(stream: TcpStream, state: Arc<Mutex<Shared>>) -> io::Result<()>
     tokio::spawn_async(async move {
         while let Some(line) = await!(rx.next()) {
             let line = line.unwrap();
-            await!(lines_tx.send_async(line));
+            await!(lines_tx.send_async(line)).unwrap();
         }
     });
 

tokio-async-await/examples/src/echo_server.rs

@@ -1,4 +1,4 @@
-#![feature(await_macro, async_await)]
+#![feature(await_macro, async_await, futures_api)]
 
 #[macro_use]
 extern crate tokio;