This project hasn't been updated in two years. A couple of active alternatives:
https://github.com/BBC-News/wraith Wraith: A responsive screenshot comparison tool.
https://github.com/garris/BackstopJS BackstopJS: visual regression testing by comparing DOM screenshots over time.
https://github.com/Huddle/PhantomCSS PhantomCSS: Visual/CSS regression testing with PhantomJS.