Update Documentation upon Electron Release about electronjs.org-old

[zcbenz]

@jlord I prefer to update the documents via web hooks, but I think neither way would work well for how we update the website now, because writing a script to push commits to repo is hard to get right and from my experience such script always tends to encounter unexpected errors after a long run.

I think we should not put electron's documents into this repo, a possible better way is to download the documents when the website is running, in following workflow:

When the website is started

1. Pull the list of Electron's releases.
2. Check what we have in _docs.
3. Download missing documents into _docs by unzipping each release's source tarball. If it is started for the first time we will download the documents of all releases.
4. Start serving.

When there is a new release of Electron

1. The website get notified via web hook.
2. Check if we already have this release in _docs, it could happen if I accidentally unpublished a release and then republished it.
3. Download the documents of new release into _docs.

The atom.io seems to work in this way, I don't know much about RoR but it might be possible to reuse code there.

[zeke]

This is a thing now! We set up a Heroku app that runs every ten minutes.

See the release script here: https://github.com/electron/electron.atom.io/blob/cbe46dd421e91d2eddbee0d46d670d8afface771/script/release