README references `config.reek` but reek's default config file is `.reek.yml`

The README says it will look for the nearest `config.reek` file, but reek's docs says reek looks for the nearest `.reek.yml` file instead (it works just fine with a `.reek.yml` in the project's root dir).

I can create a PR, but maybe I'm missing some context (was `config.reek` the default config file before?)