Use package:sky imports consistently

sky/sdk/lib/widgets/drawer_header.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/view_configuration.dart';
-import 'basic.dart';
-import 'default_text_style.dart';
-import 'theme.dart';
+import 'package:sky/theme/view_configuration.dart';
+import 'package:sky/widgets/basic.dart';
+import 'package:sky/widgets/default_text_style.dart';
+import 'package:sky/widgets/theme.dart';
 
 // TODO(jackson): This class should usually render the user's
 // preferred banner image rather than a solid background
 
 class DrawerHeader extends Component {
 
   DrawerHeader({ String key, this.children }) : super(key: key);
 
   final List<Widget> children;
 
@@ skipping 19 matching lines @@
             style: Theme.of(this).text.body2,
             child: new Flex(children, direction: FlexDirection.horizontal)
           )
         )],
         direction: FlexDirection.vertical
       )
     );
   }
 
 }