[WISHLIST] Use custom artist for mpl plotting

[iosonofabio]

What is the feature or improvement you would like to see?

Using a custom artist simplifies a few things when plotting or animating graphs in matplotlib. @tacaswell just referred me to this:

https://github.com/networkx/grave/blob/af475f04f48b8d193091cc510b447c264580b766/grave/grave.py#L221

So let's keep it in mind for the next refactoring of our plotting codebase.