Properly display YAML front matter in Markdown
Simplified version of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2906 to display the frontmatter in a formatted code block, rather than tables.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Simplified version of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2906 to display the frontmatter in a formatted code block, rather than tables.