Roll Observatory packages and add a roll script

packages/quiver/lib/src/iterables/infinite_iterable.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 30 matching lines @@
   T lastWhere(bool test(T value), {T orElse()}) =>
       throw new UnsupportedError('lastWhere');
 
   T reduce(T combine(T value, T element)) =>
       throw new UnsupportedError('reduce');
 
   List<T> toList({bool growable: true}) => throw new UnsupportedError('toList');
 
   Set<T> toSet() => throw new UnsupportedError('toSet');
 }