language: ruby
rvm:
  - '2.1.0'
  - '2.2.0'
  - '2.3.0'
  - '2.4.0'

before_install:
  - gem update bundler

language: ruby
rvm:
  - '2.1.0'
  - '2.2.0'
  - '2.3.0'
  - '2.4.0'

Fix build on Ruby 2.2.0
Fix build on Ruby 2.2.0

https://github.com/bundler/bundler/issues/3558
