Travis: install pytest-mpl as needed
Travis: install pytest-mpl as needed

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