.travis.yml in gist_updater-0.4.5 vs .travis.yml in gist_updater-0.4.6

@@ -1,8 +1,9 @@
 language: ruby
 rvm:
-  - 2.2.9
-  - 2.3.6
-  - 2.4.3
-  - 2.5.0
+  - 2.5.1
+  - 2.4.4
+  - 2.3.7
 before_install: gem install -N bundler
-before_script: bundle exec rubocop
+before_script:
+  - ./bin/validate-target-ruby-version.rb
+  - bundle exec rubocop