Roll Observatory packages and add a roll script

packages/web_components/lib/build/web_components.dart

 // 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.
 
 /// Transformer used for pub serve and pub build
 library web_components.build.web_components;
 
 import 'dart:async';
 import 'package:barback/barback.dart';
 import 'package:code_transformers/assets.dart';
@@ skipping 77 matching lines @@
             from: path.url.dirname(primaryInput.id.path));
 
         // Output the new document and bootstrap file.
         transform
             .addOutput(new Asset.fromString(primaryInput.id, doc.outerHtml));
         transform.addOutput(bootstrap);
       });
     });
   }
 }