[Tests] up to `node` `v8.2`, `v7.10`, `v6.11`, `v4.8`; newer npm breaks on older node; improve matrix
[Tests] up to `node` `v8.2`, `v7.10`, `v6.11`, `v4.8`; newer npm breaks on older node; improve matrix
ljharb/string-at,es-shims/string-at