[BUG] Notifications: Correct `transaction_url` in response
[BUG] Notifications: Correct `transaction_url` in response

```
{
  "success": true,
  "notification": {
    "account": "rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn",
    "type": "settings",
    "direction": "outgoing",
    "state": "validated",
    "result": "tesSUCCESS",
    "ledger": "9018856",
    "hash": "AE79DE34230403EA2769B4DA21A0D4D2FD7A18518DBA0A4C5B6352AFD844D22A",
    "timestamp": "2014-09-23T19:13:20.000Z",
    "transaction_url": "https://api.ripple.com/v1/transactions/AE79DE34230403EA2769B4DA21A0D4D2FD7A18518DBA0A4C5B6352AFD844D22A",
    "previous_hash": "F4ABD52AD23EDB915EA42830091A5D257FC067308FBB9D5E8D865E1B54005103",
    "previous_notification_url": "https://api.ripple.com/v1/accounts/rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn/notifications/F4ABD52AD23EDB915EA42830091A5D257FC067308FBB9D5E8D865E1B54005103",
    "next_hash": "8A0EF7B11B27FF92BFB0C2544CD533D171EF9A397053BBD6306B999ACE60B390",
    "next_notification_url": "https://api.ripple.com/v1/accounts/rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn/notifications/8A0EF7B11B27FF92BFB0C2544CD533D171EF9A397053BBD6306B999ACE60B390"
  }
}
```

xdv/ripple-rest,hserang/ripple-rest,ripple/ripple-rest,radr/radr-rest,Treefunder/ripple-rest,sparro/ripple-rest,sparro/ripple-rest,dinexcode/ripple-rest-dinex,lumberj/ripple-rest,bankonme/ripple-rest