Fixes lodash vulnerabilities by updating to latest revision

This came about because after running npm install we see the following:

found 39 high severity vulnerabilities
  run `npm audit fix` to fix them, or `npm audit` for details

Author: elroadster

package-lock.json

@@ -29,7 +29,7 @@
     "express": "^4.15.5",
     "express-validation": "^1.0.2",
     "joi": "^11.1.1",
-    "lodash": "^4.17.4",
+    "lodash": "^4.17.15",
     "morgan": "^1.9.1",
     "pdf-parse": "^1.1.1",
     "puppeteer": "^1.14.0",