add .gitlab-ci.yml

.gitlab-ci.yml

+before_script:
+  - apt-get update -qq && apt-get install -y -qq ruby
+  - ruby -v
+  - which ruby
+  - gem install bundler --no-ri --no-rdoc
+  - bundle install --jobs $(nproc) "${FLAGS[@]}"
+
+rspec:
+  script:
+    - bundle exec rspec
+
+rubocop:
+  script:
+    - bundle exec rubocop