Fixed a typo in the route factor calculation function.  Also addressed a few minor errors that were cropping up when running Michael's empirical ant travel networks.  The Resource and Nests networks appear to contain information on resource and nest location rather than an actual network, which is contained in the Roads files.  Errors still occuring when trying to open the shapefiles for Pfeier and Wilgenburg.  Perhaps these files weren't created correctly?  To Do:  Determine why igraph is inserting more nodes than needed into these shapefiles.  We should only have nodes at intersections.