Upgrade to Rust 2018

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;