Major updates (deprecating Xvfb and self-hosted cron job):

• Use GitLab Schedules to trigger test periodically

Setting up Pipeline Schedule on GitLab 10.0 in 1 step

• Deprecate Xvfb and install Google Chrome dependencies by package in the Docker image

docker pull joyzoursky/python-chromedriver:3.6

• Original image still exists but with a different tag

docker pull joyzoursky/python-chromedriver:3.6-xvfb

• Update selenium example project to use Chrome official headless mode

• Update .gitlab-ci.yml gist with example deprecating Xvfb