.travis.yml in gistory-0.1.2 vs .travis.yml in gistory-0.1.3

@@ -1,6 +1,8 @@
 sudo: false
 language: ruby
 rvm:
+  - 2.4.0
   - 2.3.3
-  - 2.2
+  - 2.2.6
+  - 2.1.10
 before_install: gem install bundler -v 1.14.3