Tidy up path handling in document_file (#464)

* Tidy up path handling in document_file

+ Improve #455

* Cargo Clippy lints

* Rename to_vec to map_to_vec

Co-authored-by: Oliver Davies <oliver@psyfer.io>

graphene/src/layers/mod.rs

@@ -189,17 +189,11 @@ impl<'a> IntoIterator for &'a Layer {
 	}
 }
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct LayerIter<'a> {
 	pub stack: Vec<&'a Layer>,
 }
 
-impl Default for LayerIter<'_> {
-	fn default() -> Self {
-		Self { stack: vec![] }
-	}
-}
-
 impl<'a> Iterator for LayerIter<'a> {
 	type Item = &'a Layer;