This point won't show up in the graph itself and can not be interacted
with. Instead it only has the purpose to attract all nodes in the graph.
This can be useful if you have unconnected nodes and want to prevent
them from floating away.
Instead the draw function now takes a parameter of type function to
which it passes the edges and nodes tables. This means the user can (and
has to) handle the drawing of the graph.
The random function is now seeded properly and uses the x, y, w, and h
parameters passed to the function to determine in what range to randomly
place the nodes.
