Corrections in audio support and Modernizr

* updated audio browser support. Source: http://html5doctor.com/native-audio-in-the-browser/
* removed the comment about Modernizr  263 not including the latest version of the HTML5 shiv and not supporting <main>. Version 2.7.0 of Modernizr fixed this

Signed-off-by: Jérôme Coupé <jercoupe@gmail.com>