DOC: clarify how to run tests in HACKING.txt
MAINT: altered mstats.sem to match stats.sem.  Closes gh-3086.

This adds a ``ddof`` keyword to the mstats version.  Output for
default ``ddof`` is unchanged.
Merge branch 'pr/3181' into master.

Reviewed at https://github.com/scipy/scipy/pull/3181
DOC: make curve_fit nomenclature same as leastsq

The curve_fit help used N for the number of data points and M for the number of parameters, but lasts which has these reversed. Fixes issue #3172
Merge pull request #3187 from alchemyst/master

DOC: make curve_fit nomenclature same as leastsq
clipped sf, pmf and cdf funs to between 0 and 1