FLUID-5516: Updated build site to match new design.

@jobara @acheetham - I've updated the build site to match the new designs. Can you check to make sure I got all the right demos and that the links all go to the right places?
@jhung, I'm feeling like the "Table of Contents" header looks very, very large. It's an h1, which I think is ok, but it just looks too big. It's almost 5 times the size of the text. What do you think about making it a bit smaller, visually?