chore(package): update codecov to version 2.3.0

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
     "@types/mocha": "2.2.41",
     "@types/node": "8.0.14",
     "@types/should": "8.3.0",
-    "codecov": "2.2.0",
+    "codecov": "2.3.0",
     "dateformat": "2.0.0",
     "execa": "0.7.0",
     "fetch-mock": "5.12.1",