Update some outdated things

* README
* Add a new contributor
* Introduce a consistent code style
It's a signal for the reader that the source parameter is unused. It is based upon the magic `_` variable that is available in Ruby (and JavaScript, Haskell and a lot of other languages) which you can assign stuff to but never read stuff out of. It's used for unused parameters.

I really like the `_bla` convention, because you can still see what this parameter *could* be used for. Useful to allow future changes.