Merge pull request #664 from aycabta/move-rubyhead-to-allow_failures

Move ruby-head to allow_failures in .travis.yml

Author: aycabta

.travis.yml

@@ -16,5 +16,6 @@ env:
 script: rake
 matrix:
   allow_failures:
+    - rvm: ruby-head
     - rvm: jruby-9.1.17.0
     - rvm: jruby-9.2.0.0