chore(package): update nyc to version 12.0.2

Closes #29

Author: greenkeeper[bot]

package.json

@@ -46,7 +46,7 @@
     "eslint": "^4.12.1",
     "mocha": "^5.0.0",
     "mock-require": "^3.0.0",
-    "nyc": "^11.4.0",
+    "nyc": "^12.0.2",
     "sinon": "^4.1.3",
     "sinon-chai": "^3.0.0"
   },