Fix broken imports in routes/__init__.pyi

This is needed by #786.

third_party/2/routes/__init__.pyi

@@ -2,8 +2,8 @@
 #
 # NOTE: This dynamically typed stub was automatically generated by stubgen.
 
-import routes.mapper
-import routes.util
+from . import mapper
+from . import util
 
 class _RequestConfig:
     def __getattr__(self, name): ...