Merge pull request #604 from aycabta/use-jruby-9.1.16.0

Use JRuby 9.1.16.0

Author: aycabta

.travis.yml

@@ -9,7 +9,7 @@ rvm:
   - 2.4.3
   - 2.5.0
   - ruby-head
-  - jruby-9.1.15.0
+  - jruby-9.1.16.0
 env:
   global:
     NOBENCHMARK=1