Improve biweight function docs
Improve biweight function docs

AustereCuriosity/astropy,DougBurke/astropy,kelle/astropy,dhomeier/astropy,pllim/astropy,mhvk/astropy,StuartLittlefair/astropy,astropy/astropy,AustereCuriosity/astropy,larrybradley/astropy,pllim/astropy,dhomeier/astropy,dhomeier/astropy,kelle/astropy,stargaser/astropy,pllim/astropy,saimn/astropy,DougBurke/astropy,astropy/astropy,MSeifert04/astropy,lpsinger/astropy,pllim/astropy,lpsinger/astropy,stargaser/astropy,larrybradley/astropy,bsipocz/astropy,funbaker/astropy,aleksandr-bakanov/astropy,stargaser/astropy,astropy/astropy,astropy/astropy,DougBurke/astropy,mhvk/astropy,StuartLittlefair/astropy,larrybradley/astropy,saimn/astropy,larrybradley/astropy,StuartLittlefair/astropy,kelle/astropy,lpsinger/astropy,MSeifert04/astropy,MSeifert04/astropy,lpsinger/astropy,larrybradley/astropy,mhvk/astropy,astropy/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,AustereCuriosity/astropy,mhvk/astropy,aleksandr-bakanov/astropy,bsipocz/astropy,StuartLittlefair/astropy,mhvk/astropy,saimn/astropy,saimn/astropy,bsipocz/astropy,dhomeier/astropy,saimn/astropy,kelle/astropy,stargaser/astropy,funbaker/astropy,kelle/astropy,funbaker/astropy,pllim/astropy,bsipocz/astropy,AustereCuriosity/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,MSeifert04/astropy,dhomeier/astropy,DougBurke/astropy,funbaker/astropy,AustereCuriosity/astropy