Add methods to Result. Bump version to 2.0 and remove deprecated features.

lib/src/result/capture_sink.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 'result.dart';
 
-/// Use [Result.captureSinkTransformer].
-@Deprecated("Will be removed in async 2.0.0.")
+/// Used by [Result.captureSink].
 class CaptureSink<T> implements EventSink<T> {
-  final EventSink _sink;
+  final EventSink<Result<T>> _sink;
 
   CaptureSink(EventSink<Result<T>> sink) : _sink = sink;
 
   void add(T value) {
     _sink.add(new Result.value(value));
   }
 
   void addError(Object error, [StackTrace stackTrace]) {
     _sink.add(new Result.error(error, stackTrace));
   }
 
   void close() {
     _sink.close();
   }
 }