Fix JRuby builds

TheSmartnik · TheSmartnik · commit 5c213a29771a · 2018-01-12T19:32:26.000+03:00
diff --git a/.travis.yml b/.travis.yml
@@ -10,7 +10,7 @@ rvm:
   - 2.2.2
   - 2.3.3
   - 2.4.1
-  - jruby-9
+  - jruby-9.1.15.0
   - rbx-3
 
 gemfile: ".travis/Gemfile"
