.travis.yml in onebox-1.8.22 vs .travis.yml in onebox-1.8.23

@@ -1,7 +1,11 @@
 language: ruby
 rvm:
-  - 2.3.1
+  - 2.2
+  - 2.3
+  - 2.4
 notifications:
   email:
     on_success: change
     on_failure: change
+script:
+  - bundle exec rubocop