Initializing CCXT with rate_limit parameter optional (default to false)

config.json.example

@@ -17,6 +17,7 @@
         "name": "bittrex",
         "key": "your_exchange_key",
         "secret": "your_exchange_secret",
+        "ccxt_rate_limit": false,
         "pair_whitelist": [
             "ETH/BTC",
             "LTC/BTC",

freqtrade/exchange/__init__.py

@@ -91,7 +91,7 @@ class Exchange(object):
                 'secret': exchange_config.get('secret'),
                 'password': exchange_config.get('password'),
                 'uid': exchange_config.get('uid', ''),
-                'enableRateLimit': True,
+                'enableRateLimit': exchange_config.get('ccxt_rate_limit', False),
             })
         except (KeyError, AttributeError):
             raise OperationalException(f'Exchange {name} is not supported')