Remove extraneous extern crate calls from chapter 4 source.

chapter-04-newmap/src/components.rs

@@ -1,7 +1,4 @@
-extern crate specs;
 use specs::prelude::*;
-extern crate specs_derive;
-extern crate rltk;
 use rltk::{RGB};
 
 #[derive(Component)]

chapter-04-newmap/src/main.rs

@@ -1,6 +1,4 @@
-extern crate rltk;
 use rltk::{Console, GameState, Rltk, RGB};
-extern crate specs;
 use specs::prelude::*;
 #[macro_use]
 extern crate specs_derive;

chapter-04-newmap/src/map.rs

@@ -1,4 +1,3 @@
-extern crate rltk;
 use rltk::{ RGB, Rltk, Console, RandomNumberGenerator };
 use super::{Rect};
 use std::cmp::{max, min};

chapter-04-newmap/src/player.rs

@@ -1,6 +1,4 @@
-extern crate rltk;
 use rltk::{VirtualKeyCode, Rltk};
-extern crate specs;
 use specs::prelude::*;
 use super::{Position, Player, TileType, xy_idx, State};