Update unittest to new package layout.

utils/tests/archive/reader_test.dart

 // Copyright (c) 2012, 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('reader_test');
 
 #import('dart:io');
-#import('../../../pkg/unittest/unittest.dart');
+#import('../../../pkg/unittest/lib/unittest.dart');
 #import('../../archive/archive.dart');
 
 final String dataPath = "utils/tests/archive/data";
 
 main() {
   test('reading a .tar.gz file', () {
     var asyncDone = expectAsync0(() {});
 
     var reader = new ArchiveReader();
     reader.format.tar = true;
@@ skipping 170 matching lines @@
   test("opening a non-existent archive", () {
     var reader = new ArchiveReader();
     reader.format.tar = true;
     reader.filter.gzip = true;
 
     expect(reader.openFilename("$dataPath/non-existent.tar.gz"),
       throwsA((e) => e is ArchiveException));
   });
 }