Bump js-yaml from 3.9.0 to 3.13.1

Bumps [js-yaml](https://github.com/nodeca/js-yaml) from 3.9.0 to 3.13.1.
- [Release notes](https://github.com/nodeca/js-yaml/releases)
- [Changelog](https://github.com/nodeca/js-yaml/blob/master/CHANGELOG.md)
- [Commits](nodeca/js-yaml@3.9.0...3.13.1)

package.json

@@ -21,7 +21,7 @@
     "express": "^4.16.3",
     "express-csp-header": "^2.3.1",
     "fs-extra": "^5.0.0",
-    "js-yaml": "^3.9.0",
+    "js-yaml": "^3.13.1",
     "request": "^2.87.0",
     "rimraf": "^2.6.2",
     "shuffle-array": "^1.0.1",