getting cluster by its name, improved tests
NMI moved to externa validations, fixed computing percision (singleton clusters does not increment precision)
skip unsupported linkages during bruteforce evolution
cluster columns by default
testing extreme caseses for precision
fixed accuracy for clusters with single item
fixed recall for cluster size eq 1
fixed f-measure for cluster size eq 1, part of logic moved to an abstract class
fixed Folkes-Mallows for cluster size eq 1
fixed Jaccard and Rand index for cluster size eq 1
added specificity
added AUC