sudo: false
language: ruby
rvm:
  - 2.3.1
before_install: gem install bundler -v 1.13.6

sudo: false
language: ruby
rvm:
  - 2.3.1
  - 2.2.0
  - 2.1.9
before_install: gem install bundler -v 1.13.6

Add support for major releases
Add support for major releases

Currently, Travis CI is only running the test suite for ruby version
`2.3.1`, but we want need some backward compatibility, so this commit
adds some other major versions (2.2.0, 2.1.9), so now whenever there
is a new PR then it will make sure our test suite passes on the all
of the major versions.
