Use latest Rubies

lowjoel · lowjoel · commit a4104aadf149 · 2016-09-10T11:16:23.000+08:00
diff --git a/.travis.yml b/.travis.yml
@@ -2,8 +2,9 @@ sudo: false
 language: ruby
 rvm:
   - 2.0.0
-  - 2.1.6
-  - 2.2.2
+  - 2.1.9
+  - 2.2.5
+  - 2.3.1
   - ruby-head
 matrix:
   allow_failures:
