Simplify demos

[robdodson]

@surma I was thinking it might make it easier to work with the project if we simplify the demos a bit.

For the AOM branch I just wrote an HTML file that includes anything I need (web components polyfills, maybe an AOM polyfill someday(?), howto-label, etc) and doesn't worry about things like %PATH%
https://github.com/GoogleChromeLabs/howto-components/blob/aom/elements/howto-checkbox/demo.html

I mainly did this because I want to be able to share the demo easily with other folks who might check out the repo and I was concerned about them getting hung up with a build step. Also on numerous occasions I've edited the demo file so it looks like the above so I could hack on something. Then when I reach a stopping point I delete all of the stuff and put things like %PATH% back so it works for the build process.

I realize the reason we have the current build setup is because of the way things live in Web Fundamentals. One idea I had was to leave the docs and everything as they are on web fundamentals, but for live demos, it could just link to our demo pages on GitHub, instead of needing to embed on the site itself.

[robdodson]

Talked with Surma about this over hangouts and we agreed that we can switch over to hosting the demos on gh-pages. For web fundamentals we'll have a button that links to the live demo. That will cut down on a lot of the weirdness in getting stuff on /web.