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:moment:20170905

Latest report for streetsupport/manchester-charter:
https://snyk.io/test/github/streetsupport/manchester-charter
StreetSupport/manchester-charter,StreetSupport/manchester-charter,StreetSupport/manchester-charter