build: update npm requirement to ^5.8.0
build: update npm requirement to ^5.8.0

Updates the requirements on [npm](https://github.com/npm/npm) to permit the latest version.
- [Release notes](https://github.com/npm/npm/releases)
- [Changelog](https://github.com/npm/npm/blob/latest/CHANGELOG.md)
- [Commits](https://github.com/npm/npm/commits/v5.8.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
ianwremmel/boilerize