gate.io: Include fee rate in order.
gate.io: Include fee rate in order.

Example order:

```
{'id': '998307286', 'datetime': '2018-07-09T17:49:43.000Z', 'timestamp': 1531158583000, 'status': 'closed', 'symbol': 'XLM/USDT', 'type': 'limit', 'side': 'sell', 'price': 0.2097, 'cost': None, 'amount': 30.14004987, 'filled': 30.14004987, 'remaining': 0.0, 'trades': None, 'fee': {'cost': 0.0113766632239302, 'currency': 'USDT'}, 'info': {'orderNumber': '998307286', 'status': 'closed', 'currencyPair': 'xlm_usdt', 'type': 'sell', 'rate': '0.2097', 'left': 0, 'amount': '0.00000000', 'initialRate': '0.2097', 'initialAmount': '30.14004987', 'filledAmount': '30.14004987', 'filledRate': 0.2097, 'feePercentage': 0.18, 'feeValue': '0.0113766632239302', 'feeCurrency': 'USDT', 'fee': '0.0113766632239302 USDT', 'timestamp': 1531158583}}
```
ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt