chore(package): update codecov to version 3.0.0

Author: greenkeeper[bot]

package.json

@@ -21,7 +21,7 @@
   },
   "devDependencies": {
     "ava": "^0.22.0",
-    "codecov": "^2.3.0",
+    "codecov": "^3.0.0",
     "commitizen": "^2.9.6",
     "conventional-changelog-atom": "^0.1.1",
     "conventional-changelog-ember": "^0.2.6",