Upgrade ruby version

![lol](https://lh5.googleusercontent.com/-XCTjn-jhIqs/UaLjrDBOd-I/AAAAAAAA8Zk/tO59vWpGfKI/w426-h240/photo.jpg)
See https://www.ruby-lang.org/en/news/2014/12/25/ruby-2-2-0-released/