chore(package): update nyc to version 15.0.1

Closes #24

Author: greenkeeper[bot]

package.json

@@ -61,7 +61,7 @@
     "eslint-plugin-jest": "^23.0.0",
     "husky": "^3.0.8",
     "jest": "^24.9.0",
-    "nyc": "^14.1.1",
+    "nyc": "^15.0.1",
     "rollup": "^1.23.1",
     "rollup-plugin-babel": "^4.3.3",
     "rollup-plugin-commonjs": "^10.1.0",