Fix some clippy warnings

src/graphics.rs

@@ -30,7 +30,7 @@ pub struct ScreenPos {
 pub type ScreenPosScalar = i16;
 
 impl ScreenPos {
-    pub fn to_sf_vec(&self) -> Vector2f {
+    pub fn to_sf_vec(self) -> Vector2f {
         Vector2f::new(self.x.into(), self.y.into())
     }
 }

src/world.rs

@@ -9,19 +9,12 @@ pub struct ChunkPos {
     y: ChunkPosScalar,
 }
 
+#[derive(Default)]
 pub struct World {
     /// The currently loaded chunks
     chunks: FnvHashMap<ChunkPos, Chunk>,
 }
 
-impl Default for World {
-    fn default() -> Self {
-        Self {
-            chunks: Default::default(),
-        }
-    }
-}
-
 impl World {
     /// Get mutable access to the tile at `pos`.
     ///