Is there any support for directed graphs?

[chrisdew]

I'm considering adding support for directed graphs, as I can't find it here.

As far as I can see, without much thinking applied, this only needs the following:

• An optional flag in the Graph constructor to allow directed graphs.
• Some minor changes in search algorithms to only follow outward edges, if the graph is a directed graph.

What are your thoughts?

All the best,

Chris.