Update .gitlab-ci.yml

.gitlab-ci.yml

-# requiring the environment of Ruby 2.3.x
-image: ruby:2.3
+image: busybox
 
-# add bundle cache to 'vendor' for speeding up builds
-cache:
-  paths:
-    - vendor/
-
-before_script:
-  - bundle install --path vendor
-
-# the 'pages' job will deploy and build your site to the 'public' path
 pages:
   stage: deploy
   script:
-    - bundle exec jekyll build -d public/
+    - echo "The site will be deployed to $CI_PAGES_URL"
   artifacts:
     paths:
       - public
-  only:
-    - master # this job will affect only the 'master' branch
+  rules:
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH