`~> 0.19` will cause us to get 0.20, 0.21, etc. With new cops that will cause the build to break. That is to say, without changing any code, it is possible to run `bundle exec rubocop` twice in a row, and have it pass the first time and fail the second.

`~> 0.19.0` will get us patches to the cops in 0.19.x, e.g. 0.19.2