.travis.yml in airborne-0.2.9 vs .travis.yml in airborne-0.2.10

@@ -1,9 +1,10 @@
 sudo: false
 language: ruby
 rvm:
   - 2.2.3
   - 2.3.1
+  - 2.4.1
 
 script: bundle exec rspec spec
 before_install:
   - gem update --system
   - gem --version