Negative amount on bitfinex orderbook

[saniales]

in exchanges/bitfinex.go change this

			// now let's create the cache
			for price, amount := range orderbookMap {
				if amount < 0 {
					orderbook.Asks = insertSort(orderbook.Asks, environment.Order{
						Value:    decimal.NewFromFloat(price),
						Quantity: decimal.NewFromFloat(amount),
					}, false)
				} else if amount > 0 {
					orderbook.Bids = insertSort(orderbook.Bids, environment.Order{
						Value:    decimal.NewFromFloat(price),
						Quantity: decimal.NewFromFloat(-amount),
					}, true)
				}
			}

to this

			// now let's create the cache
			for price, amount := range orderbookMap {
				if amount < 0 {
					orderbook.Asks = insertSort(orderbook.Asks, environment.Order{
						Value:    decimal.NewFromFloat(price),
						Quantity: decimal.NewFromFloat(-amount),
					}, false)
				} else if amount > 0 {
					orderbook.Bids = insertSort(orderbook.Bids, environment.Order{
						Value:    decimal.NewFromFloat(price),
						Quantity: decimal.NewFromFloat(amount),
					}, true)
				}
			}