Move sky/examples to sky/sdk/lib/example, and code changes to support that change. Fixes T277.

sky/sdk/lib/example/rendering/baseline.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:sky' as sky;
 
 import 'package:sky/painting/text_style.dart';
 import 'package:sky/rendering/block.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
@@ skipping 58 matching lines @@
   RenderBox root = new RenderBlock(children: [
     new RenderConstrainedBox(
       additionalConstraints: new BoxConstraints.tightFor(height: 50.0)
     ),
     getBox(1.0),
     getBox(null),
   ]);
   var b = new SkyBinding(root: root);
   // b.onFrame = b.debugDumpRenderTree;
 }