Getting rid of ruby-head and jruby head because we don't support those

Author: Nathan Sutton

.travis.yml

@@ -8,7 +8,5 @@ rvm:
   - rbx-2.0.0
   - rbx-2.1.1
   - rbx-2.2.5
-  - ruby-head
-  - jruby-head
   - 1.8.7
   - ree