Add Guardian Egyptian Web Medium to project

Soon to be used on the new fronts.

I've also included a map of the actual fonts that we use in webfonts.scss. Before we weren't passing anything to guss-webfonts(), which meant that before IE9 was loading **all** the fonts.
what does this actually create? trying to work out what `guss-webfonts` does with this (use-as?), but there doesn't seem to be as many variations of fonts as in the `webfontjson.js` below