html/gen: allow to use .md paths for internal links
internal links
html/gen: better title generation
improve markdownification
html/gen: add anchors to (sub)titles

Hm, generated main titles do not receive anchors.
fix case of nested promises

untested
add stream_drop_while
add maybe_attribute method
non-hacky handling of anchors

btw main titles will never have anchors, if not generated then anchor
is dropped anyway. It's ok.
html/gen: use titles, not filenames, in navigation
fix grammar
add CONTACT
html/gen: lowercase paths for publishing
installation info
make symlinking the 'executable' work
minor touchup
bug reporting
add hint to visit website..
html: add url_diff, my.css
add array_map_with_i