changing the doc strings of measurements.sum
correcting the measurements.sum() doc strings
small changes in the description of class hypergeom_gen
MAINT: avoid nans in logistic pdf
MAINT: avoid nans in pdfs of several distribution
TST: stop silencing the floating-point warnings
Merge pull request #2841 from EvgeniBurovski/distr_fp

improve numerical stability of several distributions
Merge pull request #2814 from djarecka/fix-.stats.hypergeom_doc

Fix .stats.hypergeom doc