Implement Container widget

Remove `align_self` and `justify_content` methods

winit/src/application.rs

@@ -1,12 +1,13 @@
 use crate::{
-    column, conversion,
+    conversion,
     input::{keyboard, mouse},
     renderer::{Target, Windowed},
-    Cache, Column, Debug, Element, Event, Length, MouseCursor, UserInterface,
+    Cache, Container, Debug, Element, Event, Length, MouseCursor,
+    UserInterface,
 };
 
 pub trait Application {
-    type Renderer: Windowed + column::Renderer;
+    type Renderer: Windowed;
 
     type Message: std::fmt::Debug;
 
@@ -282,9 +283,8 @@ where
     let view = application.view();
     debug.view_finished();
 
-    Column::new()
+    Container::new(view)
         .width(Length::Units(size.width.round() as u16))
         .height(Length::Units(size.height.round() as u16))
-        .push(view)
         .into()
 }