Add before /body:
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//gist.googlecode.com/svn/trunk/kares/script.js"></script>
<script src="//gist.googlecode.com/svn/trunk/nicerobot/5233890/replacegista.js"></script>You can then just add normal markdown references to a gist like this gist and it’ll find them and replace them with the embedded gist. Example tumblr post.
I looked at soemarko/1395926 but I didn’t want to have to use a div since Markdown already inserts a link. Also, it degrades nicely in case something with the scripts breaks. Lastly, D3 is much more fun than jQuery :P