Update RuboCop to new Gem Version

Update RuboCop to new gem version (0.23.0).
Include New RuboCop file layout specified in [this](https://github.com/bbatsov/rubocop/issues/1050) issue.

Update Rakefile to use new RuboCop class definition.
From Rubocop to RuboCop.

Add new .rubocop_todo.yml file following new RuboCop file structure.

Signed-off-by: "Jake Champlin" <jake.champlin.27@gmail.com>
@smith excellent point, but git is actually smart enough to ignore whitespace. So if you -w0 locally or add `?w=1` to the GitHub URL, you'll see the real diff. Trailing commas, on the other hand, are not whitespace chars so they will be used.

I, too, am torn: https://www.youtube.com/watch?v=sYAhku6gKQA