mention 'npm install' in the README
remove the now-unused placeholder._ template file
make citations work again

I had accidentally turned off citation handling. Run the cited() function again
over all body text. Since it inserts tags, HTML-escape the body first and in
the template turn off HTML escaping.

Also resolve internal DC Code links to the right filename. First run make_index.js
to generate a mapping from section numbers to filenames.
make an index from sections to their parents and show links to ancestor pages in the HTML files
make a footer and put Code recency information (i.e. current as of...) in it
improve rendering of the root page's title now that I've changed the root node type to <level> in the upstream code repository
make the HTML not quite so simple

Adding CSS. Basing HTML roughly off of HTML5Boilerplate.