Fix rubocop links to point to the right version.

Fixes #2 

@jrafanie or @brandondunne Please review.

Example URL:
old: http://rubydoc.info/gems/rubocop/frames/Rubocop/Cop/Style/AlignHash
new: http://rubydoc.info/gems/rubocop/0.21.0/Rubocop/Cop/Style/AlignHash