update plot method

[knaaptime]

i'm not sure it's necessary to keep but if so, it should definitely be redone. Now that we're storing geoms as part of the network, it's basically a one-liner to do

(psuedo)

access = net.aggregate(kwargs)
net.nodes_df.assign(access=access).plot(kwargs)

no need to setup a matplotlib scatter and you get all the benefits of geopandas plotting, like mapclassify classification and ability to add contextily basemap