language: ruby
sudo: false
rvm:
  - 1.9
  - 2.0
  - 2.1
  - 2.2
  - 2.3
  - 2.4

language: ruby
sudo: false
before_install:
  - gem install bundler
rvm:
  - 1.9
  - 2.0
  - 2.1
  - 2.2
  - 2.3
  - 2.4

Update bundler for Travis CI
Update bundler for Travis CI

Ruby 1.9.3 seems to be having problems on Travis. Unfortunately, it
looks like changing the default bundler may resolve it.
