Added OKCoin return interfaces for authenticated SPOT HTTP API requests.
Added OKCoin return interfaces for authenticated SPOT HTTP API requests.

thrasher-/gocryptotrader,thrasher-/gocryptotrader,thrasher-/gocryptotrader,snipesjr/gocryptotrader,jmaurice/gocryptotrader,snipesjr/gocryptotrader,thrasher-/gocryptotrader,snipesjr/gocryptotrader,thrasher-/gocryptotrader,snipesjr/gocryptotrader