.travis.yml in prometheus_exporter-0.4.10 vs .travis.yml in prometheus_exporter-0.4.11

@@ -1,7 +1,12 @@
 sudo: required
 language: ruby
 dist: trusty
 rvm:
-  - 2.5.0
+  - 2.3
+  - 2.4
+  - 2.5
+  - 2.6
 before_install: gem install bundler -v 1.16.1
 before_script: sudo sh -c 'echo 0 > /proc/sys/net/ipv6/conf/all/disable_ipv6'
+
+script: bundle exec rubocop && bundle exec rake