chore(package): update codecov to version 3.1.0 (#312)

Author: gucong3000

package.json

@@ -29,7 +29,7 @@
     "to-time": "^1.0.2"
   },
   "devDependencies": {
-    "codecov": "^3.0.4",
+    "codecov": "^3.1.0",
     "csslint": "^1.0.5",
     "eclint": "^2.7.0",
     "eslint": "^5.1.0",