Merge pull request #844 from ahorek/jruby_head

CI: move jruby-head to allowed_failures

Author: pitr-ch

.travis.yml

@@ -65,6 +65,7 @@ matrix:
 
   allow_failures:
     - rvm: ruby-head
+    - rvm: jruby-head
     - rvm: rbx-3
     - name: TruffleRuby Latest
     - name: YARD uptodate in docs