chore(deps): remove ruby 2.0 & 2.1 from CI, middleman dropped support
chore(deps): remove ruby 2.0 & 2.1 from CI, middleman dropped support

ActiveSupport requires ruby 2.2+, so middleman dropped support when this was merged: https://github.com/middleman/middleman/pull/1967
middleman/middleman-sprockets,middleman/middleman-sprockets,middleman/middleman-sprockets