Simplify "Embedding JSON-LD in HTML Documents"

@gkellogg, was there a reason why you choose such a complex example? If not, I think this is much simpler and illustrates the mechanisms just as well.

I've also removed the part which says "For text/html, text inside of the script tags does not need to be escaped." Which is wrong, see http://www.w3.org/TR/html5/scripting-1.html#restrictions-for-contents-of-script-elements

This addresses #231.