coinbase.go
func (c Client) GetSellPrice(qty int) (*pricesHolder, error) {
	return c.getPrice("sell", qty)
}
func (c Client) GetSellPrice(qty int) (*pricesHolder, error) {
	return c.getPrice("sell", qty)
}
func ( c Client ) GetSellPrice ( qty int ) ( * pricesHolder , error ) { return c . getPrice ( " " , qty ) }
// GetSellPrice gets the current BTC sell price
GetSellPrice gets the current BTC sell price