fix: package.json & package-lock.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-AJV-584908
- https://snyk.io/vuln/SNYK-JS-ANSIREGEX-1583908
- https://snyk.io/vuln/SNYK-JS-FSTREAM-174725
- https://snyk.io/vuln/SNYK-JS-HAWK-2808852
- https://snyk.io/vuln/SNYK-JS-JSONSCHEMA-1920922
- https://snyk.io/vuln/SNYK-JS-MINIMATCH-3050818
- https://snyk.io/vuln/SNYK-JS-MINIMIST-2429795
- https://snyk.io/vuln/SNYK-JS-MINIMIST-559764
- https://snyk.io/vuln/SNYK-JS-QS-3153490
- https://snyk.io/vuln/SNYK-JS-TAR-174125
- https://snyk.io/vuln/npm:cryptiles:20180710
- https://snyk.io/vuln/npm:extend:20180424
- https://snyk.io/vuln/npm:hoek:20180212
- https://snyk.io/vuln/npm:sshpk:20180409
- https://snyk.io/vuln/npm:stringstream:20180511