Ensure documentation generated from markdown resembles GitHub markdown closely.

[schuur]

Context

To easy authoring of documentation in markdown over the different projects/repositories, we need to make sure that GitHub's html preview matches the end-result generated in pact-docs.
Both the current python script and MkDocs use the standard Python Markdown module, which differs subtly from the markdown formatter GitHub is using.

Task

• Investigate extensions to python Markdown to resemble GitHub,
• Look at alternative formatters, which should also work with MkDocs.
• Implement