Updates to D graph library

[Joseph Rushton Wakeling]

Hello all,

Today I pushed a number of major (and breaking) changes to the 
master repository of the D graph library.  I've provided a brief 
summary on my blog, which also describes how to revise any 
programs to work with the new code:
http://braingam.es/2013/09/d-graph-library-updates/

I hope that these changes don't unduly inconvenience anyone 
currently using the library.  My own take was that it's worth it 
in terms of moving to a generic design and offering some new 
higher-performance graph data structures, which I'll be 
describing in more detail some time soon.

Feedback on the new code is welcome.  I would also like to offer 
thanks to all the nice people on D.learn who contributed useful 
ideas that helped with this update :-)

Thanks & best wishes,

     -- Joe