Merge pull request #11 from junaruga/feature/update-travis

Using latest version of Ruby

Author: hsbt

.travis.yml

@@ -1,6 +1,6 @@
 language: ruby
 rvm:
-  - 2.3.3
-  - 2.4.0
+  - 2.3.4
+  - 2.4.1
   - ruby-head
 before_install: gem update bundler