chore(package): update nyc to version 8.4.0 (#216)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -49,7 +49,7 @@
     "diff": "3.0.1",
     "in-publish": "2.0.0",
     "mocha": "3.1.2",
-    "nyc": "8.3.2",
+    "nyc": "8.4.0",
     "react": "15.3.2",
     "source-map-support": "0.4.6",
     "standard-version": "3.0.0",