The arguments skip.vertex, skip.edges,
and skip.arrows now work as documented.
New function nplot_legend() helps adding legends to
the figure.
New nplot() method for matrices.
New feature: Gradients.
The argument sample.edges now works as
expected.
vertex.color, vertex.size, and
vertex.nsides now accepts formulas.
edge.width now accepts formulas.
New function: locate_vertex().