chore(package): update nyc to version 15.0.1

Closes #166

Author: greenkeeper[bot]

package.json

@@ -76,7 +76,7 @@
     "lodash": "^4.17.4",
     "mocha": "^6.1.4",
     "npm-run-all": "^4.1.1",
-    "nyc": "^14.1.0",
+    "nyc": "^15.0.1",
     "prop-types": "^15.6.0",
     "react": "^16.7.0",
     "react-dom": "^16.7.0",