Modernize the package's style.

lib/src/delegate/future.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.delegate.future;
-
 import 'dart:async';
 
 /// A wrapper that forwards calls to a [Future].
 class DelegatingFuture<T> implements Future<T> {
   /// The wrapped [Future].
   final Future _future;
 
   DelegatingFuture(this._future);
 
   Stream<T> asStream() => _future.asStream();
 
   Future catchError(Function onError, {bool test(error)}) =>
     _future.catchError(onError, test: test);
 
   Future then(onValue(T value), {Function onError}) =>
     _future.then(onValue, onError: onError);
 
   Future<T> whenComplete(action()) => _future.whenComplete(action);
 
   Future timeout(Duration timeLimit, {void onTimeout()}) =>
     _future.timeout(timeLimit, onTimeout: onTimeout);
 }