Make the behaviour of infinite values consistent

[karoliskoncevicius]

Double-check and synchronize the way different tests handle Inf values.

Right now some of the non-parametric tests treat the Inf/-Inf values as highest/lowest ranks. However the behaviour for parametric tests are not fully defined. In particular when both Inf and -Inf values are present within the same group.

• [ ] t_equalvar
• [ ] t_paired
• [ ] t_onesample
• [ ] t_welch
• [ ] cor_pearson
• [ ] f_var
• [ ] oneway_equalvar
• [ ] oneway_welch
• [ ] kruskalwallis
• [ ] waerden
• [ ] bartlett
• [ ] jarquebera
• [ ] flignerkilleen
• [ ] levene
• [ ] brownforsythe
• [ ] wilcoxon_onesample
• [ ] wilcoxon_paired
• [ ] wilcoxon_twosample
• [ ] cosinor
• [ ] andersondarling