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 :(
Will revert if you feel strongly. FWIW, relevant comment from matz http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/43765