.travis.yml in milkode-1.8.8 vs .travis.yml in milkode-1.8.9

@@ -6,11 +6,14 @@
       - [e-mail]
       - [e-mail]
       
 rvm:
   # - 1.8.7
-  - 1.9.3
-  - 2.0.0
+  # - 1.9.3
+  # - 2.0.0
+  - 2.1.9
+  - 2.2.5
+  - 2.3.1
 
 sudo: required
 before_install:
   - curl --silent --location https://github.com/groonga/groonga/raw/master/data/travis/setup.sh | sh
   - gem update bundler