Add matplotlib to doctest_requires
Add matplotlib to doctest_requires

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