Revert "Upgrade RuboCop to 0.23.0"

This reverts commit 1e3e4200579fd567a53b417f15776c98d1e2650d.

Rubocop has changed their configuration structure which will break existing
config for all of our users. Until we find a strategy to deal with this, we
should not upgrade any higher.
Lock RuboCop to v0.22.0

* Update configuration link to point to the right tag of RuboCop
Extract CommentingPolicy policy object

* Extract `CommentingPolicy` object for logic around permitting
  Hound to comment on a line in a pull request