.travis.yml in test-kitchen-1.21.2 vs .travis.yml in test-kitchen-1.22.0

@@ -3,12 +3,13 @@
 services: docker
 
 language: ruby
 
 rvm:
-  - 2.3.6
-  - 2.4.3
+  - 2.3.7
+  - 2.4.4
+  - 2.5.1
   - ruby-head
 
 
 before_install:
   - gem --version
@@ -24,14 +25,14 @@
   only:
   - master
 
 matrix:
   include:
-    - rvm: 2.5.0
+    - rvm: 2.5.1
       before_install:
       # https://github.com/travis-ci/travis-ci/issues/8978
       - gem update --system
-    - rvm: 2.4
+    - rvm: 2.4.4
       # To run the proxy tests we need additional gems than what Test Kitchen normally uses
       # for testing
       gemfile: Gemfile.proxy_tests
       before_install:
         - sudo usermod -p `openssl passwd -1 'travis'` travis