Remove Ruby 2.0.0 from the list of tested Rubies
Remove Ruby 2.0.0 from the list of tested Rubies

Since Rubocop requires Ruby 2.1+ we're not going to test against Rubies
under that anymore. We're not explicitly dropping support for them,
however.

intridea/hashie,intridea/hashie,dblock/hashie,dblock/hashie