chore(package): update nyc to version 15.0.1

Closes #204

Author: greenkeeper[bot]

package.json

@@ -134,7 +134,7 @@
     "eslint": "^3.16.1",
     "mkdirp": "^0.5.1",
     "glob-fs": "^0.1.6",
-    "nyc": "^10.1.2",
+    "nyc": "^15.0.1",
     "rimraf": "^2.6.1",
     "sanitize-filename": "^1.6.1",
     "tmp": "^0.0.31",