Add browser-compatible version.

lib/resource.dart

Index: lib/resource.dart
diff --git a/lib/resource.dart b/lib/resource.dart
index 83c75c695dabd9249317861ec15cbf8691c36cb8..91c74a04493fd17d932e1fd1e42e0fde3edd05e0 100644
--- a/lib/resource.dart
+++ b/lib/resource.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2016, 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.
 
@@ -21,9 +21,10 @@
 ///                             .first;
 ///
 ///
-/// Notice: Currently this package requires `dart:io` to do the reading,
-/// so it doesn't work in the browser.
+/// Notice: Currently this library requires `dart:io` to do the reading,
+/// so it doesn't work in the browser. Use `browser_resource.dart` in the
+/// browser.
 library resource;
 
-export "src/resource.dart" show Resource;
-export "src/loader.dart" show ResourceLoader;
+export "src/io/resource.dart" show Resource;
+export "src/io/loader.dart" show ResourceLoader;