.travis.yml in cloudtasker-0.2.0 vs .travis.yml in cloudtasker-0.3.0

@@ -1,7 +1,16 @@
 ---
-sudo: false
 language: ruby
 cache: bundler
 rvm:
+  - 2.3
+  - 2.4
   - 2.5.5
 before_install: gem install bundler -v 2.0.2
+before_script: rubocop
+gemfile:
+  - gemfiles/google_cloud_tasks_1.0.gemfile
+  - gemfiles/google_cloud_tasks_1.1.gemfile
+  - gemfiles/google_cloud_tasks_1.2.gemfile
+  - gemfiles/google_cloud_tasks_1.3.gemfile
+  - gemfiles/rails_5.2.gemfile
+  - gemfiles/rails_6.0.gemfile