Add latest ruby (2.1.2)

padi · padi · commit 638c9a818f29 · 2014-06-22T23:01:19.000+08:00
https://www.ruby-lang.org/en/news/2014/05/09/ruby-2-1-2-is-released/
diff --git a/.travis.yml b/.travis.yml
@@ -1,9 +1,10 @@
 rvm:
   - 1.9.3
   - 2.0.0
+  - 2.1.2
 notifications:
     email:
       recipients:
         - neo@codingarena.in
       on_success: [change]
-      on_failure: [always]
+      on_failure: [always]
