Update unittest to new package layout.

tests/html/fileapi_test.dart

 #library('fileapi');
-#import('../../pkg/unittest/unittest.dart');
-#import('../../pkg/unittest/html_config.dart');
+#import('../../pkg/unittest/lib/unittest.dart');
+#import('../../pkg/unittest/lib/html_config.dart');
 #import('dart:html');
 
 void fail(message) {
   guardAsync(() {
     Expect.fail(message);
   });
 }
 
 DOMFileSystem fs;
 
@@ skipping 56 matching lines @@
           successCallback: expectAsync1((FileEntry e) {
             expect(e.name, equals('file4'));
             expect(e.isFile, equals(true));
           }),
           errorCallback: (e) {
             fail('Got file error: ${e.code}');
           });
       });
   });
 }