The major changes here are:

1. Inherit from `RuboCop::Cop::Base`, not `RuboCop::Cop::Cop`.
2. New auto-correction style - `extend RuboCop::Cop::AutoCorrector`,
   pass a block to `add_offense` rather than defining an `autocorrect`
   method.
3. `add_offense` no longer takes a `location` keyword argument.
4. Specs should not set `subject(:cop)` as that will be done
   automatically, and will use the config correctly.