Another round of polishing (#101)

* Implement basic refactorings

* Simplify some match statements

* Rename `ix` to `index`

If we're not going with a single letter name,
then a full word makes more sense.

* Rename `as_hex` to `to_hex`

`as_` implies lossless reinterpretation
while the function does a conversion that loses information

* Replace `for_each` with for loops

for loops are a lot easier to read and maintain.

* factor out x and y coords in Line::render

this is arguably more ergonomic

* Remove redundant `format!(format_args!())`

core/document/src/layers/polyline.rs

@@ -24,13 +24,14 @@ impl LayerData for PolyLine {
 			return;
 		}
 		let _ = write!(svg, r#"<polyline points=""#);
-		self.points.iter().for_each(|p| {
+		for p in &self.points {
 			let _ = write!(svg, " {:.3} {:.3}", p.x, p.y);
-		});
+		}
 		let _ = write!(svg, r#"" {}/>"#, self.style.render());
 	}
 }
 
+#[cfg(test)]
 #[test]
 fn polyline_should_render() {
 	let mut polyline = PolyLine {