add test for using nddata with convolve functions
add test for using nddata with convolve functions

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