Redo and add more documentation to gh-pages.

Install wintersmith globally and run `wintersmith preview` or build web and open build/gh-pages.

You'll probably notice this links to release zip files. I'd like to use github releases which for now will be a manual process:

1. Update moz central
1. Move  BETA_VERSION to STABLE_VERSION in make.js
1. Use version number from moz central for BETA_VERSION
1. Create a PR with above changes
1. `git checkout <BETA_VERSION>`
1. Run `node make dist` to generate the zip
1. Create github release
   2. add release notes
   2. attach zip generated from above
   2. mark as pre-release
1. Remove pre-release flag from previous beta release
1. Eat cake