.travis.yml in airborne-0.2.5 vs .travis.yml in airborne-0.2.6

@@ -3,11 +3,12 @@
 rvm:
   - 2.0.0
   - 2.1.0
   - 2.1.7
   - 2.2.3
+  - 2.3.1
 
-
 script: bundle exec rspec spec
 before_install:
   - gem update --system
   - gem --version
+  - gem install bundler