Roll Observatory packages and add a roll script

packages/quiver/lib/io.dart

 // Copyright 2013 Google Inc. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 58 matching lines @@
         }));
       }
     }, onDone: () {
       completer.complete(null);
     }, cancelOnError: true);
   }
   _list(dir);
 
   return futureGroup.future;
 }