Document markdown format supported

[mulka]

It seems like the documentation for Podium (neither the readme nor readthedocs page) indicates what version of markdown is supported or describe how to create a presentation file that will run in Podium. That would be helpful for potential users of Podium.

[freakboy3742]

Thanks for the suggestion - definitely a good one; and I was a little surprised to see the README doesn't include this already.

For the record, Podium is a wrapper around RemarkJS, so the markup format is whatever Remark supports.