Modernize the package's style.

lib/src/result/release_transformer.dart

+// Copyright (c) 2016, 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.
+
+import 'dart:async';
+
+import '../result.dart';
+import 'release_sink.dart';
+
+/// Use [Result.releaseTransformer] instead.
+@Deprecated("Will be removed in async 2.0.0.")
+class ReleaseStreamTransformer<T> implements StreamTransformer<Result<T>, T> {
+  const ReleaseStreamTransformer();
+
+  Stream<T> bind(Stream<Result<T>> source) {
+    return new Stream<T>.eventTransformed(source, _createSink);
+  }
+
+  static EventSink<Result> _createSink(EventSink sink) {
+    return new ReleaseSink(sink);
+  }
+}