githubbadges.herokuapp.com has been down for some time, and these badges
repeated information that was already visible on
https://github.com/dfhack/dfhack (and they weren't included in the generated
docs either).
Github's markdown parser does not permit newlines between link titles
and link text. This change removes the newlines, resulting in a less
pleasing source, but one which renders when viewed on github.
Github also requires a space between the '#' and text of headings, so
we fix that, too.
The root of the documentation tree has a different function to the short
readme we want to display on GitHub, which now links to the main docs
(or Bay12 thread, or IRC). It also renders properly on GitHub, and can
use live-updating status badges because we don't expect it to work
offline.