Make _test_tokenizer import relative so tests work on py3k.

tests/test_ctokenizer.py

@@ -28,7 +28,7 @@ try:
 except ImportError:
     CTokenizer = None
 
-from _test_tokenizer import TokenizerTestCase
+from ._test_tokenizer import TokenizerTestCase
 
 @unittest.skipUnless(CTokenizer, "C tokenizer not available")
 class TestCTokenizer(TokenizerTestCase, unittest.TestCase):

tests/test_pytokenizer.py

@@ -25,7 +25,7 @@ import unittest
 
 from mwparserfromhell.parser.tokenizer import Tokenizer
 
-from _test_tokenizer import TokenizerTestCase
+from ._test_tokenizer import TokenizerTestCase
 
 class TestPyTokenizer(TokenizerTestCase, unittest.TestCase):
     """Test cases for the Python tokenizer."""