Remove nalgebra dependency

- Implement our own `Point` and `Vector` types
  - Make `Rectangle` not generic

src/widget/button.rs

@@ -263,7 +263,7 @@ pub trait Renderer {
     fn draw(
         &mut self,
         cursor_position: Point,
-        bounds: Rectangle<f32>,
+        bounds: Rectangle,
         state: &State,
         label: &str,
         class: Class,

src/widget/checkbox.rs

@@ -182,8 +182,8 @@ pub trait Renderer {
     fn draw(
         &mut self,
         cursor_position: Point,
-        bounds: Rectangle<f32>,
-        label_bounds: Rectangle<f32>,
+        bounds: Rectangle,
+        label_bounds: Rectangle,
         is_checked: bool,
     ) -> MouseCursor;
 }

src/widget/panel.rs

@@ -90,5 +90,5 @@ where
 }
 
 pub trait Renderer {
-    fn draw(&mut self, bounds: Rectangle<f32>);
+    fn draw(&mut self, bounds: Rectangle);
 }

src/widget/radio.rs

@@ -192,8 +192,8 @@ pub trait Renderer {
     fn draw(
         &mut self,
         cursor_position: Point,
-        bounds: Rectangle<f32>,
-        label_bounds: Rectangle<f32>,
+        bounds: Rectangle,
+        label_bounds: Rectangle,
         is_selected: bool,
     ) -> MouseCursor;
 }

src/widget/slider.rs

@@ -222,7 +222,7 @@ pub trait Renderer {
     fn draw(
         &mut self,
         cursor_position: Point,
-        bounds: Rectangle<f32>,
+        bounds: Rectangle,
         state: &State,
         range: RangeInclusive<f32>,
         value: f32,

src/widget/text.rs

@@ -177,7 +177,7 @@ pub trait Renderer<Color> {
     /// [`VerticalAlignment`]: enum.VerticalAlignment.html
     fn draw(
         &mut self,
-        bounds: Rectangle<f32>,
+        bounds: Rectangle,
         content: &str,
         size: f32,
         color: Option<Color>,