HTML Elements as Custom Elements

Hello, TAG!

As discussed at our meeting last week, I started digging into reimagining
HTML elements as custom elements.

https://gist.github.com/dglazkov/5398136596f15e472332

At first blush, it looks like a bunch API design work. But <insert iraqi
information minister pic> don't panic, I think we can cover a lot of ground
if we first start with the simpler elements, like HTMLMarqueeElement.

PRs/forks are always welcome, as well as any ideas on how to structure this
project.

:DG<