Practically remove boot.js, adds the initialization from the Dart side of

pkg/polymer/lib/init.dart

+// Copyright (c) 2013, 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 that automatically initializes polymer elements without having to
+ * write a main for your application.
+ *
+ * If a polymer application is written entirely with `<polymer-element>` tags
+ * and there is no initialization code that needs to happen before these
+ * elements are created, then, instead of creating your own `main`, you can
+ * simply include a script tag loading this library:
+ *
+ *    <script type="application/dart" src="packages/polymer/init.dart">
+ *    </script>
+ *
+ * This script tag should be placed after all HTML imports on your page.
+ */
+library polymer.init;
+
+import 'package:polymer/polymer.dart';
+
+main() => initPolymer();