chore(package): update nyc to version 15.0.1

Closes #46

Author: greenkeeper[bot]

package.json

@@ -64,7 +64,7 @@
     "eslint-config-unity": "^1.0.1",
     "fake-indexeddb": "^2.1.1",
     "husky": "^2.5.0",
-    "nyc": "^14.1.1",
+    "nyc": "^15.0.1",
     "rimraf": "^2.5.4",
     "sinon": "^7.3.2",
     "validate-commit-msg": "^2.8.2"