Yeah, I was also hoping for a CMS in 18 lines of code. You could probably just about build something useful if you get opinionated enough, such as sending requests to https://cdn.rawgit.com, parsing Markdown (if you don't count libraries -- otherwise, cheat by using GitHub's Markdown API :)) and wrapping it in an html file (possibly also from rawgit).

Or, you could build a CMS around https://stackedit.io. It can apparently sync with CouchDB.