Bumps [superagent](https://github.com/visionmedia/superagent) from 5.3.1 to 6.0.0. - [Release notes](https://github.com/visionmedia/superagent/releases) - [Changelog](https://github.com/visionmedia/superagent/blob/master/HISTORY.md) - [Commits](https://github.com/visionmedia/superagent/compare/v5.3.1...v6.0.0) Signed-off-by: dependabot[bot] <support@github.com>