#1 Show edge info on Dot generated files

[Janto Dreijer]

First, I'd like to thank you for this wonderful package. Its
straightforward interface is amazing! I love working with
it. I'm using it in my MEng and the ICFP competition.

I needed the data attached to edges to show up on
images generated through pydot. Pydot currently is ot
able to do this.

I quickly hacked it to work by just adding
if (head, tail) in self.graph._edge_data:
fp.write(mid_patt % ('label', self.graph._edge_data
[(head, tail)]))
inside the pydot.Dot.save_dot method.

Most people would more likely need the weight of an
edge than the attached data. But I specifically needed
the data. It would be nice if you guys could integrate it
with your distribution.

Thanks!