don't use internal-only path when requiring promise polyfill (#4012)
don't use internal-only path when requiring promise polyfill (#4012)

see: https://github.com/zloirock/core-js/issues/138#issuecomment-161407746
gatsbyjs/gatsby,0x80/gatsby,mingaldrichgan/gatsby,fk/gatsby,0x80/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,fk/gatsby,0x80/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,fk/gatsby,mingaldrichgan/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby