cleanup the ruby code

things i did here

* [x] remove unnecessary whitespace
* [x] remove ruby warnings (ruby -w) (unused variables, ambiguous naming) 
* [x] remove hash-rockets and use new hash-syntax
* [x] remove unnecessary  `return` statements and method hashes `bla({:x => 'y'})` --> `bla(x: 'y')`
* [x] reformat with BeatifyRuby

The added `else ... nil` isn't necessary; that's implicitly added by Ruby