chore(package): update nyc to version 6.2.1

http://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -43,7 +43,7 @@
     "cz-conventional-changelog": "1.1.5",
     "in-publish": "2.0.0",
     "mocha": "2.4.5",
-    "nyc": "6.1.1",
+    "nyc": "6.2.1",
     "react": "0.14.8",
     "tslint": "3.7.1",
     "typescript": "1.8.9"