Tidy up .rubocopy.yml

This alphabetizes the configuration for rubocop.yml and preps for a
rubocop auto-config so we're not constantly hit with warnings.
Add .rubocop_todo.yml
Ignore PercentLiteralDelimiters and WordArray

Per a discussion in IRC, these rules in particular don't
appear to be valuable for Metasploit at this stage.
Also remove the offenses from the todo
Land 3587, add rubocop autoconfig