Add flake8 settings to repo

[eykd]

Since flake8 is in the tests, it would be helpful to include the required settings in the repo. I have different default settings than the defaults in my home directory, so when putting together the changes for #5, flake8 passed for me locally but failed on Travis.

[hackebrot]

Hi @eykd, thank you for getting in touch! 🙇

Poyo uses the default flake8 settings of the latest version. No exceptions 😸