As mentioned in http://redcloth.org/textile/writing-paragraph-text/#dashes
RedCloth converts double hyphens to emdashes. This causes problems in
the guides where options like --database, --full are rendered incorrectly.
This commit fixes it by customizing the emdash method in the
RedCloth::Formatters::HTML module to just return '--'. See their FAQ
http://redcloth.org/faq in the section 'How do I customize RedCloth?'