.travis.yml in honey_format-0.5.0 vs .travis.yml in honey_format-0.6.0

@@ -1,6 +1,7 @@
 language: ruby
 rvm:
   - 2.3.0
   - 2.4.0
   - 2.5.0
+  - 2.6.0-preview1
 before_install: gem install bundler -v 1.16.1