update TODO
updated README and added options to build.sh for building the website, guide, or both

and corresponding `_build/config-*` files and tweaks elsewhere
serve static content from `_site` using the new `--serve` option

experimented with using file urls so files could be read directly in the browser
(as @rdowner had done with `build-preview` in the original website),
but the `url` and `baseurl` are not inserted everywhere (and since we prefer relative links
we probably don't want them everywhere, and filesystem doesn't work nicely in `<base>`)),
so that doesn't work too well; serving is a nice and simple option
add `--install` option and updated README, so website is automatically installed to svn staging area