Add space after comma in default Quantity.__repr__
Add space after comma in default Quantity.__repr__

This since numpy is now much better in removing superfluous spaces.

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