[Tests] up to `node` `v8.8`, `v7.10`, `v6.11`, `v4.8`; improve matrix; use `nvm install-latest-npm` so new npm doesn’t break old node
[Tests] up to `node` `v8.8`, `v7.10`, `v6.11`, `v4.8`; improve matrix; use `nvm install-latest-npm` so new npm doesn’t break old node
es-shims/RegExp.prototype.flags,ljharb/RegExp.prototype.flags