Add README.md files per role

[hairmare]

The default of documenting individual roles with a markdown file is considered a best-practice and we should consider closing addressing this.

The ansible-galaxy commands init creates a default README that can be used as a basis to creating our own template. This template can then be used as an input to ansible-galaxy init --role-skeleton=/path/to/skeleton role_name (it's jinja2) enabling us to ensure consistant use of READMEs.

We might also want to consider letting the update docs probot help us remember to keep the docs up to date.