simplemarkdown starts working...
use correct split() args
wip simplemarkdown, fix bugs
better and better...
add iter_split() function, makes stuff look simpler
make iter_split and iter_split2 distinct functions
smarter iter_split and iter_split2

both will never yield None but an empty string instead
iter_split2 will not break arguments on the first separator when there
is no second separator.
header
some doc love
yielding two empty strings not needed
remove superfluous method
oops
started iter_split

dont allow missing ending separator
handle list prefixes with no text better
handle header better