kramdown
kramdown is a fast, pure Ruby Markdown superset converter, using a strict syntax definition and supporting several common extensions.
Ruby › Markdown Processors: “Kramdown is yet-another-markdown-parser but fast, pure Ruby, using a strict syntax definition and supporting several common extensions.”
Markdown › Libraries > Ruby: “kramdown is a fast, pure Ruby Markdown superset converter, using a strict syntax definition and supporting several common extensions.”