.travis.yml in surrender-0.8.4 vs .travis.yml in surrender-0.9.0

@@ -1,5 +1,7 @@
 language: ruby
 rvm:
   - 1.9.3
+  - 2.0.0
+  - 2.1.0
+  - ruby-head
   - jruby-19mode # JRuby in 1.9 mode
-  - rbx-19mode