Update Tokio to Rust 2018 (#1082)

tokio-sync/src/lib.rs

@@ -1,15 +1,17 @@
 #![doc(html_root_url = "https://docs.rs/tokio-sync/0.1.5")]
-#![deny(missing_debug_implementations, missing_docs, unreachable_pub)]
+#![deny(
+    missing_debug_implementations,
+    missing_docs,
+    unreachable_pub,
+    rust_2018_idioms
+)]
 #![cfg_attr(test, deny(warnings))]
+#![doc(test(no_crate_inject, attr(deny(rust_2018_idioms))))]
 
 //! Asynchronous synchronization primitives.
 //!
 //! This crate provides primitives for synchronizing asynchronous tasks.
 
-extern crate fnv;
-#[macro_use]
-extern crate futures;
-
 macro_rules! debug {
     ($($t:tt)*) => {
         if false {