chore(package): update nyc to version 8.4.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -77,7 +77,7 @@
     "karma-webpack": "1.8.0",
     "mkdirp": "0.5.1",
     "mocha": "3.1.2",
-    "nyc": "8.3.2",
+    "nyc": "8.4.0",
     "phantomjs-prebuilt": "2.1.13",
     "rimraf": "2.5.4",
     "rollup": "0.36.3",