Kruskal Wallis test

refactoring updates for Kruskal Wallis test and added that test to the
unit testing code.
stats.pl

Routines cope with multi-dimensional lists (lists of lists etc)
Commiting ignore

Ignoring .DS_Store file
Deleting DS_Store
Docstrings

Added docstrings (human readable names) to tests ready for insertion
into Salstat.