How to update ruby version?

i am getting rubocop linter errors so i tried installing rubocop but it seems like my ruby version is not up to date. is there a recommended process for updating ruby?

ERROR: Error installing rubocop:
rubocop requires Ruby version >= 2.1.0.
Joeys-MBP:appacademy-online-rspec-1 joeyfeng$ ruby -v
ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin16]