Npm dependency updates for v2.52.7

[sp3nx0r]

Ran into these findings when using SDK v2.52.7 and evaluating against Snyk. Might want to bump these versions up in case anyone is using similar tooling and has questions. Vulns don't look terribly impactful to SDK so we waived requiring a fix before using (i.e. pinning to the non vuln versions), but would be nice to see these get the bumps in later SDK version. Cheers

https://snyk.io/vuln/npm:tough-cookie:20170905
https://snyk.io/vuln/npm:stringstream:20180511
https://snyk.io/vuln/npm:hoek:20180212
https://snyk.io/vuln/npm:sshpk:20180409