Shaffer Post-hoc test error

[ghost]

I noticed that the Shaffer Post-hoc test doesn't work (nothing happens if you click on apply). I tried to call it in the source code, but something seems to be missing:
In nonparametric_tests.py
tmp = S(k - j)
NameError: global name 'S' is not defined

[armando-fandango]

Just fixed this and several other bugs. Sending pull request.