.travis.yml in pub_grub-0.4.1 vs .travis.yml in pub_grub-0.4.2

@@ -2,6 +2,7 @@
 language: ruby
 rvm:
   - 2.3
   - 2.4
   - 2.5
+  - 2.6
 before_install: gem install bundler -v 1.16.1