A lot of examples have accumulated, but over the years many of them have disappeared or moved on.  I was looking at the source code for the examples to learn anything that I might later find useful on my own site; noting which sites have disappeared, changed addresses, or migrated to other systems was a natural byproduct.

This change does the following:

*   Remove sites that no longer exist or no longer use Hakyll.
*   Remove sites whose source code is no longer public.
*   Updated addresses for sites and/or source code repositories.
*   Change `http` addresses to `https` addresses when possible.
*   There are no more Hakyll 3 sites; they have all moved to Hakyll 4, migrated to other systems, or disappeared.