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

sky/examples/stocks/lib/stock_list.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 'package:sky/framework/components/fixed_height_scrollable.dart';
-import 'package:sky/framework/fn.dart';
-import 'stock_data.dart';
-import 'stock_row.dart';
-
-class Stocklist extends FixedHeightScrollable {
-  String query;
-  List<Stock> stocks;
-
-  Stocklist({
-    Object key,
-    this.stocks,
-    this.query
-  }) : super(key: key);
-
-  List<UINode> buildItems(int start, int count) {
-    var filteredStocks = stocks.where((stock) {
-      return query == null ||
-             stock.symbol.contains(new RegExp(query, caseSensitive: false));
-    });
-    itemCount = filteredStocks.length;
-    return filteredStocks
-      .skip(start)
-      .take(count)
-      .map((stock) => new StockRow(stock: stock))
-      .toList(growable: false);
-  }
-}