add gitlab cd to deploy to heroku

.gitlab-ci.yml

+stages:
+  - deploy
+
+Deployment:
+  image: ruby:2.4
+  stage: deploy
+  before_script:
+    - gem install dpl
+    - wget -qO- https://cli-assets.heroku.com/install-ubuntu.sh | sh
+  script:
+    - dpl --provider=heroku --app=$HEROKU_APPNAME --api-key=$HEROKU_APIKEY
+    - export HEROKU_API_KEY=$HEROKU_APIKEY
+    - heroku run --app $HEROKU_APPNAME migrate
+  environment:
+    name: production
+    url: $HEROKU_APP_HOST
+

Procfile

+web: gunicorn superlists.wsgi --log-file -