Mann-Whitney is not about medians in general

I will populate this repository over time. In the meantime start with this gist: https://gist.github.com/adrianolszewski/2cec75678e1183e4703589bfd22fa8b2 This refers also to Kruskal-Wallis and Friedman test.

PS: this is much incomplete. I will provide more codes and explanations soon.