Fix Table.sort to work with a tuple of keys.
Fix Table.sort to work with a tuple of keys.

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