Mou is a Markdown editor - with a difference: where most, if not all, currently available Markdown editors are almost all for general writers, Mou is different: It's for Web developers. Syntax highlighting, live preview, sync scroll, fullscreen mode, auto save, powerful actions, auto pair, custom themes and CSS, HTML and PDF export, enhanced CJK support. I know, it's exactly the app you want.
Math support. It's disabled by default, check "Help" > "Math Syntax Help" to see how to enable it.
Improved HTML export templates for better viewing on iOS devices.
Changed Tomorrow theme's selection color from #cccccc to #ffffff so that the selection text won't become illegible when the window looses focus. Please note Mou won't overwrite your old themes automatically (to keep your customized themes safe). If you want to use the new themes, you need to delete the old themes files under ~/Library/Application Support/Mou/Themes/ folder manually, and then relaunch Mou to take effect.
Disabled SmartyPants substitutions. The OS X now built-in text substitutions feature, it's more flexible than the hard-coded SmartyPants. ( > System Preferences > Language & Text>Text > Use symbol and text substitution)
"Help" - "Markdown Syntax Reference" updated for the Footnotes syntax.