More rubocop

@localshred follow up from the last PR. This gets us nearly all the way to rubocop-completeness, but more importantly, it makes the tests run again, which I broke in the last PR :(
> The easier that software can be understood by the maintainers, the better.

Totally agree with this, with the caveat that software should also be easily understood by occasional contributors; I think sticking to an accepted community-driven style guide provides a great deal of the latter without sacrificing the former too much.