Update to test package, make test work on dart2js.

test/iterable_zip_test.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.
 
 import "dart:collection";
 import "package:collection/iterable_zip.dart";
-import "package:unittest/unittest.dart";
+import "package:test/test.dart";
 
 /// Iterable like [base] except that it throws when value equals [errorValue].
 Iterable iterError(Iterable base, int errorValue) {
   return base.map((x) => x == errorValue ? throw "BAD" : x);
 }
 
 main() {
   test("Basic", () {
     expect(new IterableZip([[1, 2, 3], [4, 5, 6], [7, 8, 9]]),
            equals([[1, 4, 7], [2, 5, 8], [3, 6, 9]]));
@@ skipping 85 matching lines @@
            throwsA(equals("BAD")));
   });
 
   test("Error after first end", () {
     expect(new IterableZip([[1, 2, 3],
                             [4, 5, 6],
                             iterError([7, 8, 9, 10], 10)]),
            equals([[1, 4, 7], [2, 5, 8], [3, 6, 9]]));
   });
 }