use JRuby 9.1.6.0

Author: hsbt

.travis.yml

@@ -8,7 +8,7 @@ rvm:
   - 2.3.1
   - ruby-head
   - jruby-1.7.20
-  - jruby-9.1.5.0
+  - jruby-9.1.6.0
   - jruby-head
 before_install:
   - gem install bundler --no-document -v '~> 1.13.3'