chore(travis): drop Node 0.11 build since 0.12 is out
chore(travis): drop Node 0.11 build since 0.12 is out

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