[Security] Bump superagent from 3.6.3 to 3.8.3
[Security] Bump superagent from 3.6.3 to 3.8.3

Bumps [superagent](https://github.com/visionmedia/superagent) from 3.6.3 to 3.8.3. **This update includes security fixes.**
- [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/v3.6.3...v3.8.3)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
danielfsousa/express-rest-es2017-boilerplate,danielfsousa/express-rest-es2017-boilerplate,danielfsousa/express-rest-es2017-boilerplate