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

sky/examples/rendering/transform.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/rendering/box.dart';
-import 'package:sky/rendering/flex.dart';
-import 'package:sky/rendering/sky_binding.dart';
-import 'package:vector_math/vector_math.dart';
-
-void main() {
-  RenderDecoratedBox green = new RenderDecoratedBox(
-    decoration: new BoxDecoration(backgroundColor: const sky.Color(0xFF00FF00))
-  );
-  RenderConstrainedBox box = new RenderConstrainedBox(
-    additionalConstraints: new BoxConstraints.tight(const Size(200.0, 200.0)),
-    child: green
-  );
-
-  Matrix4 transform = new Matrix4.identity();
-  RenderTransform spin = new RenderTransform(
-      transform: transform, child: box);
-  spin.rotateZ(1.0);
-
-  RenderFlex flex = new RenderFlex();
-  flex.add(spin);
-  new SkyBinding(root: flex);
-}