.travis.yml in hako-2.11.1 vs .travis.yml in hako-2.12.0

@@ -1,9 +1,11 @@
 language: ruby
 sudo: false
 rvm:
-  - 2.3.4
-  - 2.4.1
+  - 2.3.8
+  - 2.4.6
+  - 2.5.5
+  - 2.6.3
   - ruby-head
 before_install:
   - gem update --system # https://github.com/rubygems/rubygems/pull/1819
   - gem install bundler
 matrix: