New advertising page

Big redesign of the /advertising page.  

[huge screenshot for reference](http://i.imgur.com/DWgyyju.png)

You can safely ignore the first commit, as it is just the commit from this PR that I never got around to pushing out prior to this: https://github.com/reddit/reddit-plugin-about/pull/39.  This also depends on https://github.com/reddit/reddit-public/pull/2347 and https://github.com/reddit/reddit-plugin-gold/pull/31

There are obviously a lot of stylistic changes, but the ones I'm most concerned with are the ones in python, specifically:

* sourcing ad links from a subreddit
* sourcing almost all other text content on the page from a few different wikis

Having spent a larger portion of my time thus far doing design work, my python chops are still rough, so pay extra attention there please.

:eyeglasses: @ajacksified @spladug @umbrae @bsimpson63
You could format these as `self.banner = sections.get('banner')`