Mq orientation

[aFarkas]

This implements (orientation: portrait|landscape) into our matchMedia polyfill.

[Wilto]

I’m still worried about the additional overhead of shimming media queries. It was the first thing on my mind as I was reading http://codepen.io/Tigt/blog/when-responsive-images-get-ugly the other day. There are a lot of really cool MQ things on the horizon, which—in theory—would all be available to Picturefill when using matchMedia. By shimming MQ, we’re limiting Picturefill, and committing to playing catch-up—adding to our code weight and ongoing responsibilities.