.travis.yml in persist-0.1.3 vs .travis.yml in persist-1.0.0

@@ -1,6 +1,7 @@
 language: ruby
 rvm:
+  - ruby-head
+  - 2.1
   - 2.0.0
   - 1.9.3
   - jruby-19mode
-  - rbx-19mode