chore(package): update nyc to version 5.1.1

http://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -35,7 +35,7 @@
     "jshint": "^2.8.0",
     "metrics": "^0.1.9",
     "mocha": "^2.3.2",
-    "nyc": "^4.0.1",
+    "nyc": "^5.1.1",
     "optional-dev-dependency": "^1.1.0",
     "tcp-port-used": "^0.1.2",
     "uuid": "^2.0.1",