rename mocks to mock

src/tile.rs

@@ -1,6 +1,6 @@
 use crate::AnimationFrames;
 use crate::image::Image;
-use crate::mocks;
+use crate::mock;
 
 #[derive(Debug, Eq, PartialEq)]
 pub struct Tile {
@@ -82,8 +82,8 @@ fn test_tile_to_string() {
         name: Some("chequers".to_string()),
         wall: false,
         animation_frames: vec![
-            mocks::image::chequers_1(),
-            mocks::image::chequers_2(),
+            mock::image::chequers_1(),
+            mock::image::chequers_2(),
         ]
     }.to_string();