This is a small exporter based on the Markdown exporter already existing in Org mode. It should support the features listed here.

You can install ox-gfm using elpa. It's available on melpa:

M-x package-install ox-gfm

This package adds an Org mode export backend for GitHub Flavored Markdown. You can read more about Org mode exporting here.

Exporting to Github Flavored Markdown is available through Org mode's export dispatcher once ox-gfm is loaded. Alternatively, exporting can be triggered by calling the (autoloaded) function M-x org-gfm-export-to-markdown.

If you want to automatically load ox-gfm along with Org mode, then you can add this snippet to your Emacs configuration:

(eval-after-load "org"
  '(require 'ox-gfm nil t))