[WIP] We need a typographic scale

I started investigating setting up a typographic scale, but I'm not so sure that using the sass plugin based on Tim Brown's work is the best idea. I've did some work here, but I am not satisfied with how it turned out. 

My main goal for this PR is to merge the two typo sheets together and get something that would make a default page look great with little effort.

What do you think?