Adds the viewport width and height as a :before pseudo element on the body to help with obtaining values for responsive breakpoints
Use the bookmarklet to quickly test any site. Get it here: http://izilla.com.au/git/izilla.mq.debugger.bookmarklet.html
Or include izilla.mq.debug.bookmarklet.min.js in your page after the opening body tag, and trigger it with a querystring parameter of mqdebug=true