There is also a live version at http://iphylo.org/~rpage/wikihistoryflow. If you enter the name of a Wikipedia page the tool will display the edit history with columns representing page versions and individual contributors (people and bots) distinguished by different colours.
This tool will fall over for pages with a lengthy history of edits, and requires a web browser that can support SVG, but it's a fun visualisation, and may inspire someone to do this properly.