Fix padding on Sky home screen scrollable list

sky/sdk/lib/widgets/card.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import '../theme/colors.dart' as colors;
 import '../theme/edges.dart';
 import 'basic.dart';
 import 'material.dart';
 import "theme.dart";
 
 class Card extends Component {
   Card({ String key, this.child, this.color }) : super(key: key);
 
   final Widget child;
   final Color color;
 
   Color get materialColor {
     if (color != null)
       return color;
     switch (Theme.of(this).brightness) {
       case ThemeBrightness.light:
         return colors.White;
       case ThemeBrightness.dark:
         return colors.Grey[800];
     }
   }
 
   Widget build() {
     return new Container(
-      margin: const EdgeDims(8.0, 8.0, 0.0, 8.0),
+      margin: const EdgeDims.all(4.0),
       child: new Material(
         color: materialColor,
         edge: MaterialEdge.card,
         level: 2,
         child: new ClipRRect(
           xRadius: edges[MaterialEdge.card],
           yRadius: edges[MaterialEdge.card],
           child: child
         )
       )
     );
   }
 }