feat(sandbox): use new `vm` API
feat(sandbox): use new `vm` API

Although `vm.createScript` still exists in current versions of Node.js,
the API documentation doesn't reference anymore
(see https://nodejs.org/dist/latest-v4.x/docs/api/vm.html).

We're now using `vm.Script` instead.

BREAKING CHANGE: use `vm.Script` instead of `vm.createScript`

KlausTrainer/sandbox.js