remove state generic from a lot of things

src/widget/rect.rs

@@ -27,8 +27,8 @@ impl Rect {
     }
 }
 
-impl<State: 'static> Widget<State> for Rect {
-    fn draw(&mut self, painter: &mut Painter<State>) {
+impl Widget for Rect {
+    fn draw(&mut self, painter: &mut Painter) {
         painter.primitive(RectPrimitive {
             color: self.color,
             radius: self.radius,
@@ -37,11 +37,11 @@ impl<State: 'static> Widget<State> for Rect {
         });
     }
 
-    fn desired_width(&mut self, _: &mut SizeCtx<State>) -> Len {
+    fn desired_width(&mut self, _: &mut SizeCtx) -> Len {
         Len::rest(1)
     }
 
-    fn desired_height(&mut self, _: &mut SizeCtx<State>) -> Len {
+    fn desired_height(&mut self, _: &mut SizeCtx) -> Len {
         Len::rest(1)
     }
 }