Don't test pypy on travis
Don't test pypy on travis

Bachmann1234/marshmallow,jmcarp/marshmallow,etataurov/marshmallow,marshmallow-code/marshmallow,mwstobo/marshmallow,xLegoz/marshmallow,jmcarp/marshmallow,VladimirPal/marshmallow,quxiaolong1504/marshmallow,maximkulkin/marshmallow,daniloakamine/marshmallow,dwieeb/marshmallow,0xDCA/marshmallow,bartaelterman/marshmallow,Tim-Erwin/marshmallow,0xDCA/marshmallow