only deny warnings in tests to fix docs.rs

src/lib.rs

@@ -33,7 +33,7 @@
 //! }
 //! ```
 #![doc(html_root_url = "https://docs.rs/hyper-tls/0.3.0")]
-#![deny(warnings)]
+#![cfg_attr(test, deny(warnings))]
 #![deny(missing_docs)]
 #![deny(missing_debug_implementations)]