[igraph] double headed and curving edges in tkplot

[Jarrett Byrnes]

A second question (apologies if this is a lot).  tkplot() seems to  
allow for curved arrows when a vertex points to itself.

1) Is there a way to make other edges bow or curve.  Specifically, I  
have two vertexes, each with a directed path from one to the other.   
I wish the user to be able to see these as two separate paths, and  
hence want them to bow out a little bit.

2) Can one make a double-headed edge?  What is the proper attribute  
for this?

3) Can one have a graph both with double-headed edges and have  
reciprocal edges as in 1) above?

Thanks!  I'm trying to sort through the documentation on attributes,  
but it seems somewhat sparse.  This package is wonderful, though!   
Thanks so much!

-Jarrett