.travis.yml in ruby-short_url-0.2.0 vs .travis.yml in ruby-short_url-0.3.0

@@ -1,8 +1,11 @@
 language: ruby
+cache: bundler
 rvm:
-  - 2.2.0
-  - 2.1.0
-  - 2.0.0
+  - 2.0
+  - 2.1
+  - 2.2
+  - 2.3.3
+  - 2.4.0
 addons:
   code_climate:
     repo_token: 357da37cbdcc472b4b33ba5f6e8a6fcc14ebcb41bb951b5133c547818ad6fbb3