language: ruby
rvm:
  - 2.1.10
  - 2.2.6
  - 2.3.3
  - 2.4.0
  - jruby-9.1.8.0

matrix:
  allow_failures:
    - rvm:
        - ruby-head
        - rbx-2

language: ruby
rvm:
  - 2.2.6
  - 2.3.3
  - 2.4.0
  - jruby-9.1.8.0

matrix:
  allow_failures:
    - rvm:
        - ruby-head
        - rbx-2

Remove unsupported Ruby 2.1 from Travis CI config
Remove unsupported Ruby 2.1 from Travis CI config

More info [here](https://www.ruby-lang.org/en/news/2017/04/01/support-of-ruby-2-1-has-ended/).
