YAML vs GitLab CI syntax

Hey,

I did not feel like baking this into a full PR, but I thought instead of doing YAML magic here:

# Template for all the stages stages
.docker-build: &docker-build
  script:
    - ./build.sh
  artifacts:
    expire_in: 1 day
    paths:
      - variables

you can use GitLab CI's default keyword?

This would essentially rid you of having to do YAML-specific magic with <<: *docker-build and instead allow you to keep it clean and simple. As far as I can see, that is the exact functionality you are after? Let me know what you think.