Github did this using the HTML canvas element.
This specification defines the 2D Context for the HTML canvas element. The 2D Context provides objects, methods, and properties to draw and manipulate graphics on a canvas drawing surface.
If you use a browser inspector, you see inside every list element a div with a canvas element.
<div class="participation-graph">
<canvas class="bars" data-color-all="#F5F5F5" data-color-owner="#F5F5F5" data-source="/mxcl/homebrew/graphs/owner_participation" height="80" width="640"></canvas>
</div>
With CSS (z-index, position...) you can put that canvas in the background of a li element or table, in your case.
Do a search about jquery pluggins that fit your requirement.
Hope this pointers help you to achieve that.