Critical and high vulnerability from npm audit

[garethf89]

Npm Audit has 1 critical vulnerability and 3 high

This is causing build pipelines to fail.

Packages with issues are:

mock => Growl https://npmjs.com/advisories/146

method-overrride => https://npmjs.com/advisories/538

Express - https://npmjs.com/advisories/526

Updates to fix:

"express": "4.17.1",

"method-override": "2.3.8",

"mocha": "4.0.1",