Adds @HtmlImport with both dynamic and transformer based implementations. Still need an HtmlInliner…

lib/custom_element_proxy.dart

Index: lib/custom_element_proxy.dart
diff --git a/lib/custom_element_proxy.dart b/lib/custom_element_proxy.dart
index f9df88f6e0b5447b3c0769dd2810d6911196a434..01e63d5c3e7618d1c1ccdaddfc67d1d3ac8b5943 100644
--- a/lib/custom_element_proxy.dart
+++ b/lib/custom_element_proxy.dart
@@ -1,6 +1,8 @@
 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
+library web_components.custom_element_proxy;
+
 import 'package:initialize/initialize.dart';
 import 'interop.dart';