Roll Observatory packages and add a roll script

quiver/lib/src/iterables/count.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,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-part of quiver.iterables;
-
-/**
- * Returns an infinite [Iterable] of [num]s, starting from [start] and
- * increasing by [step].
- */
-Iterable<num> count([num start = 0, num step = 1]) => new _Count(start, step);
-
-class _Count extends InfiniteIterable<num> {
-  final num start, step;
-
-  _Count(num this.start, num this.step);
-
-  Iterator<num> get iterator => new _CountIterator(start, step);
-
-  // TODO(justin): return an infinite list for toList() and a special Set
-  // implmentation for toSet()?
-}
-
-class _CountIterator implements Iterator<num> {
-  final num _start, _step;
-  num _current;
-
-  _CountIterator(num this._start, this._step);
-
-  num get current => _current;
-
-  bool moveNext() {
-    _current = (_current == null) ? _start : _current + _step;
-    return true;
-  }
-}