2018.11.22
Fixed memory leaks in kcluster and treecluster in src/cluster.c, and in
Hierarchical and KMeans in src/command.c; these memory leaks occurred when
memory allocation failed.
Fixed a bug in the distancematrix function Bio/Cluster/__init__.py, where the 
weight argument was not properly initialized if it had the default value None,
causing the function to fail.
