language: ruby
sudo: false
branches:
  only:
    - master
rvm:
  - 2.1
  - 2.2
  - 2.3
  - 2.4

language: ruby
sudo: false
branches:
  only:
    - master
rvm:
  - 2.2.7
  - 2.3
  - 2.4

Drop support of ruby 2.1
Drop support of ruby 2.1

Latest rack gem requires ruby >= 2.2.2.
