Rid off duplicated to_json #72

Before:
```json
"{\"_id\":{\"$oid\": \"53321cff06f2942c38000001\"},\"name\":\"Miller Friesen\",\"email\":\"federico_littel@bartell.net\",\"city\":\"Lake Turnertown\",\"company\":\"Zemlak, Pollich and Cole\"}"
```

After:
```json
{"_id":{"$oid": "53321cff06f2942c38000001"},"name":"Miller Friesen","email":"federico_littel@bartell.net","city":"Lake Turnertown","company":"Zemlak, Pollich and Cole"}
```