Fix styling

I tried to make it such that we pass the rubocop tests, to make it easy to have consistent formatting. For now we have two exceptions:

* **Class/module level documentation** We don't have this yet, and to write this just for rubocop conformance felt like yak shaving ;)
* **Define methods with parentheses** We currently follow seatttle.rb formatting, which imho is just as good, so saw no need to fix this.