chore(travis): update Yarn to v1.12.1 (#1508)
chore(travis): update Yarn to v1.12.1 (#1508)


carbon-design-system/carbon-components,joshblack/carbon-components-react,carbon-design-system/carbon-components,carbon-design-system/carbon-components,joshblack/carbon-components-react,carbon-design-system/carbon-components-react,carbon-design-system/carbon-components-react