Upgrade escape-string-regexp to 4.x

https://github.com/sindresorhus/escape-string-regexp/releases/tag/v3.0.0
https://github.com/sindresorhus/escape-string-regexp/releases/tag/v4.0.0

Since tapjs#67 got stuck due to
increasing the minimum node version from 10 to 12, here's updating the
same package only within the existing node 10 support.

Author: stianjensen

package-lock.json

@@ -25,7 +25,7 @@
     "index.js"
   ],
   "dependencies": {
-    "escape-string-regexp": "^2.0.0"
+    "escape-string-regexp": "^4.0.0"
   },
   "devDependencies": {
     "bluebird": "^3.7.2",