Move unittest from lib to pkg.

tests/html/fileapi_test.dart

 #library('fileapi');
-#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();
   window.webkitRequestFileSystem(Window.TEMPORARY, 100, (fs) {
     // FIXME: add types to callback arguments after migration to wrapperless dart:html.
 
     test('getDirectory', () {
       expect(() => fs.root.getDirectory('directory1', {'x': true}, (e) {}),
              throws);
@@ skipping 37 matching lines @@
           flags: {'create': true},
           successCallback: expectAsync1((e) {
             expect(e.name, equals('file3'));
           }),
           errorCallback: expectAsync1((e) {
             expect(false, 'Got file error: ${e.code}');
           }, count:0));
     });
   });
 }