Merge pull request #261 from aycabta/use-jruby-9.1.16.0

Use JRuby 9.1.16.0

Author: hsbt

.travis.yml

@@ -8,7 +8,7 @@ rvm:
   - 2.4.3
   - 2.5.0
   - ruby-head
-  - jruby-9.1.15.0
+  - jruby-9.1.16.0
   - jruby-head
 before_script:
   - unset JRUBY_OPTS