Matt: GeoPy and Structure_Graph

GeoPy: Uses the GeoPy package, which can automatically compute distances
between Longitude/Latitude pairs.

Structure_Graph: Copies from stuff from Jitse (and Python3 corrects it)
and then I use the k_core command to remove all the edges which lead to
a dead-end.  Then I draw some PDF files with maps-- warning, these get
rather large and slow.