Remove try_from feature.

examples/hello_world.rs

@@ -1,5 +1,3 @@
-#![feature(try_from)]
-
 use std::{convert::TryFrom, env, process::exit};
 
 use futures::Future;

src/lib.rs

@@ -2,7 +2,6 @@
 
 #![deny(missing_debug_implementations)]
 #![deny(missing_docs)]
-#![feature(try_from)]
 
 use std::{convert::TryInto, str::FromStr, sync::{Arc, Mutex}};