Move unittest from lib to pkg.

tests/html/typing_test.dart

 #library('TypingTest');
-#import('../../lib/unittest/unittest.dart');
-#import('../../lib/unittest/html_config.dart');
+#import('../../pkg/unittest/unittest.dart');
+#import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 main() {
   useHtmlConfiguration();
 
   test('NodeList', () {
     List<Node> asList = window.document.queryAll('body');
     // Check it's Iterable
     int counter = 0;
     for (Node node in window.document.queryAll('body')) {
@@ skipping 10 matching lines @@
     // Check it's Iterable.
     int counter = 0;
     for (StyleSheet styleSheet in window.document.styleSheets) {
       counter++;
     }
 
     // There is one style sheet from the unittest framework.
     Expect.equals(1, counter);
   });
 }