chore(package): update nyc to version 15.1.0

Closes #75

Author: greenkeeper[bot]

package.json

@@ -51,7 +51,7 @@
     "graphql": "^14.5.8",
     "husky": "^3.0.5",
     "mocha": "^6.2.0",
-    "nyc": "^14.1.1",
+    "nyc": "^15.1.0",
     "prettier": "^1.19.1",
     "ts-node": "^8.5.4",
     "typescript": "^3.7.2"