Remove old code for old-style class
Remove old code for old-style class

On Python 3 classes are always new-style :)
pllim/astropy,aleksandr-bakanov/astropy,DougBurke/astropy,mhvk/astropy,MSeifert04/astropy,StuartLittlefair/astropy,astropy/astropy,dhomeier/astropy,MSeifert04/astropy,mhvk/astropy,pllim/astropy,bsipocz/astropy,astropy/astropy,mhvk/astropy,pllim/astropy,StuartLittlefair/astropy,saimn/astropy,dhomeier/astropy,bsipocz/astropy,lpsinger/astropy,MSeifert04/astropy,funbaker/astropy,lpsinger/astropy,mhvk/astropy,lpsinger/astropy,DougBurke/astropy,bsipocz/astropy,stargaser/astropy,astropy/astropy,stargaser/astropy,saimn/astropy,larrybradley/astropy,funbaker/astropy,pllim/astropy,astropy/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,saimn/astropy,bsipocz/astropy,stargaser/astropy,DougBurke/astropy,StuartLittlefair/astropy,dhomeier/astropy,astropy/astropy,StuartLittlefair/astropy,larrybradley/astropy,aleksandr-bakanov/astropy,saimn/astropy,lpsinger/astropy,funbaker/astropy,dhomeier/astropy,larrybradley/astropy,mhvk/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,pllim/astropy,lpsinger/astropy,funbaker/astropy,MSeifert04/astropy,saimn/astropy,larrybradley/astropy,larrybradley/astropy,DougBurke/astropy,stargaser/astropy