Modernize the package's style.

test/stream_group_test.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.
 
-library async.test.stream_group_test;
-
 import 'dart:async';
 
 import 'package:async/async.dart';
 import 'package:test/test.dart';
 
 main() {
   group("single-subscription", () {
     var streamGroup;
     setUp(() {
       streamGroup = new StreamGroup<String>();
@@ skipping 697 matching lines @@
       controller.close();
 
       await streamGroup.close();
       expect(events, equals(["one", "two", "three", "four", "five", "six"]));
     });
   });
 }
 
 /// Wait for all microtasks to complete.
 Future flushMicrotasks() => new Future.delayed(Duration.ZERO);