.travis.yml in fluent-plugin-redis-0.3.3 vs .travis.yml in fluent-plugin-redis-0.3.4

@@ -2,11 +2,13 @@
 services:
   - redis-server
 rvm:
   - 2.1
   - 2.2
-  - 2.3.3
-  - 2.4.0
+  - 2.3
+  - 2.4
+  - 2.5.3
+  - 2.6.0
 gemfile:
   - gemfiles/fluentd_v0.14.gemfile
   - Gemfile
 before_install:
   - gem update bundler