.travis.yml in oxr-0.4.0 vs .travis.yml in oxr-0.5.0

@@ -1,7 +1,6 @@
 language: ruby
 rvm:
-  - 2.1.10
-  - 2.2.6
-  - 2.3.3
+  - 2.2.7
+  - 2.3.4
   - 2.4.1
 before_install: gem install bundler -v 1.14.6