Move unittest from lib to pkg.

tests/html/events_test.dart

 #library('EventsTest');
-#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('TimeStamp', () {
     Event event = new Event('test');
 
     int timeStamp = event.timeStamp;
     Expect.isTrue(timeStamp > 0);
   });
@@ skipping 37 matching lines @@
     invocationCounter = 0;
     element.on['test'].dispatch(event);
     Expect.equals(1, invocationCounter);
   });
   test('InitMouseEvent', () {
     DivElement div = new Element.tag('div');
     MouseEvent event = document.$dom_createEvent('MouseEvent');
     event.$dom_initMouseEvent('zebra', true, true, window, 0, 1, 2, 3, 4, false, false, false, false, 0, div);
   });
 }