Fix minor docs error for ascii.write (closes #978)
Fix minor docs error for ascii.write (closes #978)

This would be good for 0.2.2.
mhvk/astropy,bsipocz/astropy,bsipocz/astropy,stargaser/astropy,dhomeier/astropy,AustereCuriosity/astropy,funbaker/astropy,joergdietrich/astropy,stargaser/astropy,tbabej/astropy,funbaker/astropy,MSeifert04/astropy,lpsinger/astropy,aleksandr-bakanov/astropy,astropy/astropy,pllim/astropy,larrybradley/astropy,joergdietrich/astropy,tbabej/astropy,StuartLittlefair/astropy,tbabej/astropy,AustereCuriosity/astropy,kelle/astropy,StuartLittlefair/astropy,funbaker/astropy,MSeifert04/astropy,saimn/astropy,kelle/astropy,dhomeier/astropy,DougBurke/astropy,kelle/astropy,lpsinger/astropy,aleksandr-bakanov/astropy,AustereCuriosity/astropy,kelle/astropy,tbabej/astropy,mhvk/astropy,pllim/astropy,larrybradley/astropy,bsipocz/astropy,stargaser/astropy,stargaser/astropy,DougBurke/astropy,larrybradley/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,pllim/astropy,dhomeier/astropy,tbabej/astropy,larrybradley/astropy,MSeifert04/astropy,DougBurke/astropy,dhomeier/astropy,saimn/astropy,bsipocz/astropy,mhvk/astropy,pllim/astropy,astropy/astropy,astropy/astropy,aleksandr-bakanov/astropy,funbaker/astropy,mhvk/astropy,larrybradley/astropy,AustereCuriosity/astropy,lpsinger/astropy,joergdietrich/astropy,DougBurke/astropy,aleksandr-bakanov/astropy,astropy/astropy,pllim/astropy,kelle/astropy,astropy/astropy,saimn/astropy,MSeifert04/astropy,lpsinger/astropy,joergdietrich/astropy,saimn/astropy,dhomeier/astropy,saimn/astropy,lpsinger/astropy,mhvk/astropy,StuartLittlefair/astropy,AustereCuriosity/astropy,joergdietrich/astropy