Added
- Added `RateLimitError`.
Changed
- `ping` property of `BitTurkClient` raises `RateLimitError`.
- `server_datetime` property of `BitTurkClient` raises `RateLimitError`.
- `exchange_info` property of `BitTurkClient` raises `RateLimitError`.
- `tickers` property of `BitTurkClient` raises `RateLimitError`.
- `get_orderbook` method of `BitTurkClient` raises `RateLimitError`.
- `get_transactions` method of `BitTurkClient` raises `RateLimitError`.