doc update to CCDData
doc update to CCDData

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