miniblog.

One cute feature of markdown I'd not noticed before: there's no syntax for images *without* a description (i.e. alt text). 

My favourite pull requests are PRs that are obviously correct after you've read the description.

I'm a fan of simple issue trackers. A description, comments, and maybe a small integration with something. Given this, perhaps it makes sense to build your own? You get a bespoke solution, and focusing on your main project prevents feature creep.