.travis.yml in swagger-diff-1.0.5 vs .travis.yml in swagger-diff-1.1.0

@@ -1,5 +1,13 @@
 language: ruby
 cache: bundler
+rvm:
+  - 2.0
+  - 2.1.9
+  - 2.2.5
+  - 2.3.1
+before_install:
+  - gem update --system
+  - rvm @global do gem install bundler
 branches:
   only:
     - master