Affinity Propagation Clustering

 Implements Affinity Propagation clustering introduced by Frey and
 Dueck (2007) <DOI:10.1126/science.1136800>. The algorithms are largely
 analogous to the 'Matlab' code published by Frey and Dueck.
 The package further provides leveraged affinity propagation and an
 algorithm for exemplar-based agglomerative clustering that can also be
 used to join clusters obtained from affinity propagation. Various
 plotting functions are available for analyzing clustering results.