Move unittest from lib to pkg.

tests/html/location_test.dart

 #library('LocationTest');
-#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('location hash', () {
       final location = window.location;
       Expect.isTrue(location is Location);
 
       // The only navigation we dare try is hash.
       location.hash = 'hello';
       var h = location.hash;
       Expect.equals('#hello', h);
     });
 }