Hopefully fixed a bug if the rich nodes are not connected at all.
Added additional topological metrics for the rich club.
Changed the behavior of selection of the reference set of links in the
denominator to be more elegant and expandable, as well as to insert a
nan and print a flag if the number of desired links is smaller than the
number available (typically looking for P links on a sparse graph.)
Bug fixes and making sure local reference sets do not draw more links
from a node than it has room for to point to other nodes in the club.
Bug fix