This is intended to fix #50, at least temporarily.

I've dug out the last non-split version of the reference and, with a help of a small Ruby script, generated a landing page, which superficially resembles the old reference, but instead of the actual contents, links to the chapters of the new reference.

This approach relies on the Markdown->HTML converter generating anchoring ids for section headers in the particular backward-compatible way, as well as on unchanging section headers in the new reference, i.e.

1. If the markdown generator changes in the future so that its header_text->anchor_id generation no longer matches the old behaviour, then the page becomes useless. This can be worked around by using a pre-generated static html page instead of Markdown.
2. If sections are renamed in the new reference, the fragment parts of redirection links on the landing page would no longer match. But at least, the links would still lead to the correct chapter pages.