prettify debug with .gist and colors - but see below.

conditional loading of modules is apparently broken or NYI
or something, so at the moment we just have a commented out
version of that and a fallback.
output debug info as well as <kbd class="todo">

for not-yet-implemented formattingcodes.
render zero-width comments as nothingness.
render D<...|...;...> as proper definitions, but no list yet
replace prelude array with heredoc string
fix unimplemented formattingcodes
implement =nested blocks
implement output named block.
Merge pull request #2 from timo/improvements

implement lots of things