.travis.yml in mshard-0.5.1 vs .travis.yml in mshard-0.6.0

@@ -1,10 +1,12 @@
 language: ruby
 sudo: false
 rvm:
   - ruby-head
-  - 2.2.5
-  - 2.3.1
-  - 2.4.0
+  - '2.2.5'
+  - '2.3.1'
+  - '2.4.0'
+  - '2.4.2'
+  - '2.5.0'
 before_install:
   - gem update --system
   - gem install bundler