chore(package): update nyc to version 14.1.0

Closes #120

Author: greenkeeper[bot]

package.json

@@ -64,7 +64,7 @@
     "flow-bin": "^0.77.0",
     "flow-copy-source": "^2.0.2",
     "mkdirp": "^0.5.1",
-    "nyc": "^13.1.0",
+    "nyc": "^14.1.0",
     "postcss-at-rules-variables": "^0.1.6",
     "postcss-cli": "^6.1.1",
     "postcss-custom-properties": "7.0.0",