Merge branch 'ci' into 'master'

Enable CI

See merge request !1

.gitlab-ci.yml

+docs:
+  stage: test
+  image: davidhrbac/docker-mdcheck:latest
+  allow_failure: true
+  script:
+  - mdl -r ~MD013 *.md
+
+shellcheck:
+  stage: test
+  image: davidhrbac/docker-shellcheck:latest
+  script:
+  - which shellcheck || apt-get update && apt-get install -y shellcheck
+  - shellcheck eb scripts/*.sh scripts/lib/*