add test_gravitational_redshift
add test_gravitational_redshift

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