chore(package): update codecov to version 2.3.1

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
   "devDependencies": {
     "@types/form-data": "2.2.0",
     "@types/mocha": "2.2.43",
-    "codecov": "2.3.0",
+    "codecov": "2.3.1",
     "dateformat": "3.0.1",
     "execa": "0.8.0",
     "fetch-mock": "5.13.1",