list and rank refs
recur of tree
initial ordering of nodes
basic display of nodes
initial layout
show basic edges
proper column layout (upside down, uncentered)
pack rows if all parents are more than one rank away
change order
parametrize gap
update todo list
improved appearance with thicker lines and anti aliasing
draw splines instead of straight lines
cleanup duplicate code
improve splines
further improve splines and reduce gaps
added refs to graph
make nodes more compact
implemented better scrolling and key bindings
add license