remove some unnecessary imports and call them inline

src/tile.rs

@@ -1,6 +1,4 @@
-use crate::{AnimationFrames, from_base36, ToBase36, optional_data_line};
-use crate::image::Image;
-use crate::mock;
+use crate::{AnimationFrames, Image, from_base36, ToBase36, optional_data_line};
 
 #[derive(Debug, Eq, PartialEq)]
 pub struct Tile {
@@ -109,8 +107,8 @@ fn test_tile_to_string() {
         name: Some("chequers".to_string()),
         wall: None,
         animation_frames: vec![
-            mock::image::chequers_1(),
-            mock::image::chequers_2(),
+            crate::mock::image::chequers_1(),
+            crate::mock::image::chequers_2(),
         ],
         colour_id: None
     }.to_string();