pkg/watcher: prepare for 0.9.3

pkg/watcher/example/watch.dart

 // Copyright (c) 2013, 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.
 
 /// Watches the given directory and prints each modification to it.
 library watch;
 
-import 'dart:io';
-
 import 'package:path/path.dart' as p;
 import 'package:watcher/watcher.dart';
 
 main(List<String> arguments) {
   if (arguments.length != 1) {
     print("Usage: watch <directory path>");
     return;
   }
 
   var watcher = new DirectoryWatcher(p.absolute(arguments[0]));
   watcher.events.listen((event) {
     print(event);
   });
 }