Move examples to //sky/sdk/example

sky/sdk/example/stocks2/lib/stock_arrow.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 'dart:math' as math;
 import 'dart:sky' as sky;
 
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
 import 'package:sky/theme/colors.dart' as colors;
@@ skipping 55 matching lines @@
 
     return new Container(
       child: arrow,
       width: kSize,
       height: kSize,
       margin: const EdgeDims.symmetric(horizontal: 5.0)
     );
   }
 
 }