Ugly, but gets the job done.

Used CSS borrowed at https://github.com/sindresorhus/github-markdown-css/blob/a77a701f48674d9868863e270916743a8d3ee6fb/github-markdown.css and slightly modified it.

![catchup_io_and_ugly__but_gets_the_job_done__by_exalted__pull_request__25__catchupio_catchup-web](https://cloud.githubusercontent.com/assets/314398/3791551/f693cb2e-1b43-11e4-8885-91f0178439bc.jpg)

![catchup_io](https://cloud.githubusercontent.com/assets/314398/3791555/0c34bea2-1b44-11e4-9df4-7867ad207ea0.jpg)

--
/cc: @as-cii 
There's a lot of boilerplate code which we could avoid using sass, for example I think we might group together all these `.markdown-body` into a single SCSS scope.

I haven't a strong position on this, thus you can keep this as–is if you believe this is maintainable.