Improve comment concerning _mask property
Improve comment concerning _mask property

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