Fix CI for Ruby 2.5.1

sds · sds · commit a0c97cd83711 · 2018-03-31T19:54:57.000-07:00
Suggested workaround for the time being: travis-ci/travis-ci#9383 (comment)
diff --git a/.travis.yml b/.travis.yml
@@ -16,6 +16,7 @@ before_script:
 
 before_install:
   - gem update --system
+  - gem install bundler
 
 script:
   - bundle exec rspec
