Refactored BTCMarkets authentication code.
Refactored BTCMarkets authentication code.

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