chore: use node 6 on travis CI
chore: use node 6 on travis CI

neokyox/angular-input-masks,assisrafael/angular-input-masks,smilight/angular-input-masks,neokyox/angular-input-masks,smilight/angular-input-masks,wesleifreitas/angular-input-masks,assisrafael/angular-input-masks,wesleifreitas/angular-input-masks