Adding ability to have sub styles of the landing page

Front-matter example:

	---
	layout: landing
	sub-style: {SubStyleName}
	---

CSS Naming:

	/css/{SubStyleName}.landing.css
Adding landing page w/ modules similar to wireframes.

Utilizes substyles mod added in commit 8782c2a to produce a landing
page that resembles the wireframe found at http://bit.ly/1gvtEBG
Merge branch 'gh-pages' of https://github.com/p2pu/school-of-webmaking into gh-pages
Merge pull request #1 from fuzzyfox/gh-pages

Better landing page template + wireframed modules landing page