.travis.yml in enter-rockstar-0.1 vs .travis.yml in enter-rockstar-0.2

@@ -1,7 +1,10 @@
----
 sudo: false
 language: ruby
-cache: bundler
 rvm:
+  - 2.3.8
+  - 2.4.5
+  - 2.5.5
   - 2.6.2
-before_install: gem install bundler -v 2.0.1
+before_install:
+  - gem install bundler
+  - gem update --system