Modernize the package's style.

lib/src/result/capture_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 'capture_sink.dart';
+
+/// Use [Result.captureTransformer] instead.
+@Deprecated("Will be removed in async 2.0.0.")

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

Just @Deprecated("in async 2.0.0")
The Deprecated class has a toString method that adds "will be removed" before
the text.

[nweiz, 2016/03/08 20:23:40]

I'm mostly concerned with how it appears in dartdoc, where it just includes the
literal annotation contents:
https://www.dartdocs.org/documentation/http_parser/2.2.0/http_parser/WebSocke...

+class CaptureStreamTransformer<T> implements StreamTransformer<T, Result<T>> {
+  const CaptureStreamTransformer();
+
+  Stream<Result<T>> bind(Stream<T> source) {
+    return new Stream<Result<T>>.eventTransformed(source, _createSink);
+  }
+
+  static EventSink _createSink(EventSink<Result> sink) {
+    return new CaptureSink(sink);
+  }
+}