Unify page structure between guide and front page

[dherman]

The guide has a generic description of Cargo ("Cargo downloads your...") as its heading at the top. The two pages should look more like screens of the same app. This might just mean eliminating that heading, or pulling it into the beginning of the guide text itself. And there should be a standard header that brands every screen in the app identically.

[alexcrichton]

I've prepared http://alexcrichton.com/cargo/ (the gh-pages of my cargo repo), does that look along the lines of that you were thinking?