better gh-pages publishing

[stephenturner]

may obviate the need for the git deploy subtree madness

https://github.com/blog/2228-simpler-github-pages-publishing

[stephenturner]

Wow. This is much better. Need No need for the whole subtree push to gh-pages. To do:

• [ ] update CONTRIBUTING.markdown with how to on building in docs instead of _site
• [ ] update CONTRIBUTING.markdown to specifically mention how you must add exclude docs (not docs/) from website build, otherwise you get a recursive file copy error (can't copy directory into itself).
• [ ] update CONTRIBUTING.markdown with screenshot (eg below) from the post describing this feature
• [ ] remove the deploy bit from .gitconfig
• [ ] find/replace _site/ for docs/ in any readme/contributing/etc kinds of meta-documentation

@vpnagraj - i'll fix the above, but if you pull in changes you'll no longer have to worry about the subtree push.

[stephenturner]

@vpnagraj forget all of this. found something better. will update shortly.

[stephenturner]

@vpnagraj review commit message in a6437c06631593bd3d80668912ef77ce9780ecb8, pull in changes. this allows us to ignore _site/, which gets clobbered every time we rebuild.