Merge pull request #66 from fastify/greenkeeper/ajv-6.0.0

Update ajv to the latest version 🚀

Author: mcollina

package.json

@@ -34,7 +34,7 @@
     "uglify-es": "^3.2.2"
   },
   "dependencies": {
-    "ajv": "^5.5.2",
+    "ajv": "^6.0.0",
     "fast-safe-stringify": "^1.2.1"
   }
 }