added note indicating minimum cython version required
added note indicating minimum cython version required

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