run black over stubs, add checking to travis

django-stubs-generated/urls/utils.pyi

@@ -1,5 +1,4 @@
 from typing import Any, Callable, Optional, Tuple, Union
 
-
 def get_callable(lookup_view: Union[Callable, str]) -> Callable: ...
 def get_mod_func(callback: str) -> Tuple[str, str]: ...