Upgrade to Rust 2018

Cargo.toml

@@ -2,6 +2,7 @@
 name = "tvrs"
 version = "0.1.0"
 authors = ["Thomas Forgione <thomas@forgione.fr>"]
+edition = "2018"
 
 [dependencies]
 clap = "2.32.0"

src/lib.rs

@@ -193,7 +193,7 @@ impl MultiScreen {
 
                 screens.push(Screen::from_line(line));
 
-            } else if let Some(mut last) = screens.last_mut() {
+            } else if let Some(last) = screens.last_mut() {
 
                 // Get the first thing
                 let split = line.split_whitespace().collect::<Vec<_>>();

src/tv.rs

@@ -1,6 +1,3 @@
-extern crate clap;
-extern crate tvrs;
-
 use clap::{Arg, App};
 use tvrs::MultiScreen;