chore(travis): run CI on docker
chore(travis): run CI on docker

yagitoshiro/power-assert,saneyuki/power-assert,yagitoshiro/power-assert,twada/power-assert,twada/power-assert,falsandtru/power-assert,power-assert-js/power-assert,saneyuki/power-assert,falsandtru/power-assert,power-assert-js/power-assert