Use new kramdown convention for inline math
Use new kramdown convention for inline math

$$ x $$
rather than
$ x $

This also helps avoid headaches for authors of financial documents/books

GitbookIO/kramed,gdbooks/kramed,GitbookIO/kramed,Ponyshow/pony-render,emilbayes/kramed,martindale/kramed,GerHobbelt/kramed,martindale/kramed,GerHobbelt/kramed,gdbooks/kramed,emilbayes/kramed