chore(package): update prebuildify to version 2.9.1 (#109)

Author: greenkeeper[bot]

package.json

@@ -26,6 +26,6 @@
   },
   "devDependencies": {
     "mocha": "~5.2.0",
-    "prebuildify": "~2.8.0"
+    "prebuildify": "~2.9.1"
   }
 }