fix: package.json to reduce vulnerabilities
fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/npm:superagent:20170807

Latest report for royriojas/react-starter-kit:
https://snyk.io/test/github/royriojas/react-starter-kit
royriojas/react-starter-kit,royriojas/react-starter-kit