chore(package): update codecov to version 3.7.0

Closes #65

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
   },
   "devDependencies": {
     "ava": "2.4.0",
-    "codecov": "3.6.1",
+    "codecov": "3.7.0",
     "nyc": "15.0.0",
     "standard-version": "7.0.1",
     "xo": "0.24.0"