chore(package): update nyc to version 15.1.0

Closes #7

Author: greenkeeper[bot]

package.json

@@ -64,7 +64,7 @@
     "lodash.uniq": "^4.5.0",
     "lodash.uniqwith": "^4.5.0",
     "mocha": "^6.1.4",
-    "nyc": "^14.0.0",
+    "nyc": "^15.1.0",
     "uniq": "^1.0.1",
     "uniqs": "^2.0.0"
   },