use pre-installed version of rubyies as much as possible

gfx · gfx · commit d2ed586212c3 · 2014-08-09T09:40:56.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -2,7 +2,7 @@ language: ruby
 rvm:
   - 1.9.3
   - 2.0.0
-  - 2.1.0
+  - 2.1.1
   - rbx-2
   - jruby-19mode
 script: bundle exec rake test
