describe how famous preserves semantic HTML

This tweet pointed out a very common misconception about Famo.us that I wanted to debunk
https://twitter.com/nathfisher/status/463853749073477632

Famous is no worse for the semantic value of a website/webapp than previous methods, but unless you spend enough time with it, you don't realize this. To make sure people don't avoid famous over this misconception, I wanted to address it in the Render Tree guide.

I may have been a little wordy. So edits to reduce it's length are welcome. 

"Je n’ai fait celle-ci plus longue que parce que je n’ai pas eu le loisir de la faire plus courte."
-- Blaise Pascal