update .travis.yml to use wheels for sphinx and matplotlib
update .travis.yml to use wheels for sphinx and matplotlib

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