Make crate compile on Rust stable

Rocket meanwhile works on Rust stable, so there is no reason to be
limited to nightly.

examples/fairing.rs

@@ -1,4 +1,3 @@
-#![feature(proc_macro_hygiene, decl_macro)]
 use std::error::Error;
 
 use rocket::http::Method;

examples/guard.rs

@@ -1,4 +1,3 @@
-#![feature(proc_macro_hygiene, decl_macro)]
 use std::error::Error;
 use std::io::Cursor;
 

examples/json.rs

@@ -1,8 +1,6 @@
 //! This example is to demonstrate the JSON serialization and deserialization of the Cors settings
 //!
 //! Note: This requires the `serialization` feature which is enabled by default.
-#![feature(proc_macro_hygiene, decl_macro)]
-
 use rocket_cors as cors;
 
 use crate::cors::{AllowedHeaders, AllowedOrigins, CorsOptions};

examples/manual.rs

@@ -1,4 +1,3 @@
-#![feature(proc_macro_hygiene, decl_macro)]
 use std::io::Cursor;
 
 use rocket::error::Error;

examples/mix.rs

@@ -3,7 +3,6 @@
 //! In this example, you typically have an application wide `Cors` struct except for one specific
 //! `ping` route that you want to allow all Origins to access.
 
-#![feature(proc_macro_hygiene, decl_macro)]
 use rocket::error::Error;
 use rocket::http::Method;
 use rocket::response::Responder;

rust-toolchain

@@ -1 +0,0 @@
-nightly

tests/fairing.rs

@@ -1,5 +1,4 @@
 //! This crate tests using `rocket_cors` using Fairings
-#![feature(proc_macro_hygiene, decl_macro)]
 use rocket::http::hyper;
 use rocket::http::Method;
 use rocket::http::{Header, Status};

tests/guard.rs

@@ -1,5 +1,4 @@
 //! This crate tests using `rocket_cors` using the per-route handling with request guard
-#![feature(proc_macro_hygiene, decl_macro)]
 use rocket_cors as cors;
 
 use rocket::http::hyper;

tests/headers.rs

@@ -1,5 +1,4 @@
 //! This crate tests that all the request headers are parsed correctly in the round trip
-#![feature(proc_macro_hygiene, decl_macro)]
 use std::ops::Deref;
 
 use rocket::http::hyper;

tests/manual.rs

@@ -1,5 +1,4 @@
 //! This crate tests using `rocket_cors` using manual mode
-#![feature(proc_macro_hygiene, decl_macro)]
 use rocket::http::hyper;
 use rocket::http::Method;
 use rocket::http::{Header, Status};

tests/mix.rs

@@ -2,7 +2,6 @@
 //!
 //! In this example, you typically have an application wide `Cors` struct except for one specific
 //! `ping` route that you want to allow all Origins to access.
-#![feature(proc_macro_hygiene, decl_macro)]
 use rocket::http::hyper;
 use rocket::http::{Header, Method, Status};
 use rocket::local::blocking::Client;