fix: upgrade commander from 2.16.0 to 2.20.3

Snyk has created this PR to upgrade commander from 2.16.0 to 2.20.3.

See this package in NPM:
https://www.npmjs.com/package/commander

See this project in Snyk:
https://app.snyk.io/org/cheshirecode/project/217d4f10-72ee-44eb-9250-d9c13b4b149d?utm_source=github&utm_medium=upgrade-pr

package.json

@@ -33,7 +33,7 @@
   },
   "prepublishOnly": "npm test && npm test:integration",
   "dependencies": {
-    "commander": "^2.16.0"
+    "commander": "^2.20.3"
   },
   "devDependencies": {
     "coveralls": "^3.0.2",

yarn.lock

@@ -319,9 +319,10 @@ combined-stream@1.0.6, combined-stream@~1.0.5:
   dependencies:
     delayed-stream "~1.0.0"
 
-commander@^2.16.0:
-  version "2.16.0"
-  resolved "https://registry.yarnpkg.com/commander/-/commander-2.16.0.tgz#f16390593996ceb4f3eeb020b31d78528f7f8a50"
+commander@^2.20.3:
+  version "2.20.3"
+  resolved "https://registry.yarnpkg.com/commander/-/commander-2.20.3.tgz#fd485e84c03eb4881c20722ba48035e8531aeb33"
+  integrity sha512-GpVkmM8vF2vQUkj2LvZmD35JxeJOLCwJ9cUkugyk2nuhbv3+mJvpLYYt+0+USMxE+oj+ey/lJEnhZw75x/OMcQ==
 
 concat-map@0.0.1:
   version "0.0.1"