.travis.yml in prorate-0.1.0 vs .travis.yml in prorate-0.3.0

@@ -1,5 +1,15 @@
-sudo: false
-language: ruby
 rvm:
-  - 2.2.5
-before_install: gem install bundler -v 1.12.5
+- 2.2.5
+- 2.3.3
+- 2.4.1
+
+services:
+- redis
+
+dist: trusty # https://docs.travis-ci.com/user/trusty-ci-environment/
+sudo: false
+cache: bundler
+
+# Travis permits the following phases: before_install, install, after_install, before_script, script, after_script
+script:
+  - bundle exec rspec