chore(package): update nyc to version 13.3.0

Closes #7

Author: greenkeeper[bot]

package.json

@@ -15,7 +15,7 @@
     "codecov": "^1.0.1",
     "cross-env": "^3.1.3",
     "doctoc": "^1.2.0",
-    "nyc": "^8.4.0",
+    "nyc": "^13.3.0",
     "standard": "^8.5.0",
     "uglify-js": "^2.6.4",
     "umd": "^3.0.1"