.travis.yml in kaiser-ruby-0.7.1 vs .travis.yml in kaiser-ruby-0.8

@@ -1,7 +1,8 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.3.7
-  - 2.4.4
-  - 2.5.1
-before_install: gem install bundler -v 1.16.1
+  - 2.3.8
+  - 2.4.5
+  - 2.5.5
+  - 2.6.2
+before_install: gem install bundler