Modernize the package's style.

lib/src/future_group.dart

Index: lib/src/future_group.dart
diff --git a/lib/src/future_group.dart b/lib/src/future_group.dart
index 02ff185ca74adc9261ec5cb58cd69249ae336206..cb4ac777e169f49b793aeb8c6a7ddb3064bb5ea0 100644
--- a/lib/src/future_group.dart
+++ b/lib/src/future_group.dart
@@ -2,8 +2,6 @@
 // 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.future_group;
-
 import 'dart:async';
 
 /// A collection of futures waits until all added [Future]s complete.
@@ -35,7 +33,7 @@ class FutureGroup<T> implements Sink<Future<T>> {
   Future<List<T>> get future => _completer.future;
   final _completer = new Completer<List<T>>();
 
-  /// Whether this group is waiting on any futures.
+  /// Returns `true` if this group isn't waiting on any futures.

[Lasse Reichstein Nielsen, 2016/03/08 10:40:37]

A getter is no different from a (final) field.
I'd prefer to document it like a filed, that is: as a property, not a function.
Returning is something that functions do - it's describing the *behavior* of the
function, not what it *is*.

[nweiz, 2016/03/08 20:23:39]

Done.

   bool get isIdle => _pending == 0;
 
   /// A broadcast stream that emits a `null` event whenever the last pending