Empty `__init__.py` files are ignored

[sobolevn]

Thanks for this plugin. It is really useful!

We have configured it like so:

accept-encodings = utf-8

But, when creating empty __init__.py file and running flake8 check, there is no error. Magic comment is missing from __init__.py.

So, this is a bug report.

[tk0miya]

I think magic comment is not needed for empty files because it does not have any content. I did it intentionally.

[sobolevn]

So, can we make it configurable?