.travis.yml in mui-sass-0.5.0 vs .travis.yml in mui-sass-0.5.9

@@ -1,11 +1,11 @@
 language: ruby
 
 rvm:
   - 2.0.0
-  - 2.1
-  - 2.2
-  - 2.3.0
+  - 2.1.9
+  - 2.2.5
+  - 2.3.1
 
 before_install: gem install bundler
 
 sudo: false