Font-Smoothing test

Hi there,

I've adapted [Zoltan Du Lac's font-smoothing detection](http://www.useragentman.com/blog/2009/11/29/how-to-detect-font-smoothing-using-javascript/) into a V3 test.

Thought it might be useful to submit it here.

This is my first submission to Modernizr, so any feedback/code reviews would be much appreciated.