exchanges/kraken,bittrex,gemini: Resolve Kraken panic, lint corrections, Bittrex batch tickers, set Gemini order limits and update tradable pairs (#1372)

* fix kraken, batch bittrex, fix lint

* surprise gemini!

* thought this happened automatically

* fix before shazbert sees

* fixes annoying atoi bug

* rm futures from gemini

* lint

* bittrex UpdatedAt, gemini Limits, stats relook

* STATS used HARDEN!(improve stats package)

* Whoopsies in your Daisies

* rm RWMutex, json stringeroo

* fixes additional index issues 😆 😭

exchanges/kraken/kraken_wrapper.go

@@ -1727,12 +1727,15 @@ func (k *Kraken) GetFuturesContractDetails(ctx context.Context, item asset.Item)
 		} else {
 			underlyingStr = underlyingBase[1]
 		}
-		usdIndex := strings.Index(underlyingStr, "usd")
+		usdIndex := strings.LastIndex(strings.ToLower(underlyingStr), "usd")
+		if usdIndex <= 0 {
+			log.Warnf(log.ExchangeSys, "%v unable to find USD index in %v to process contract", k.Name, underlyingStr)
+			continue
+		}
 		underlying, err = currency.NewPairFromStrings(underlyingStr[0:usdIndex], underlyingStr[usdIndex:])
 		if err != nil {
 			return nil, err
 		}
-
 		var s, e time.Time
 		if result.Instruments[i].OpeningDate != "" {
 			s, err = time.Parse(time.RFC3339, result.Instruments[i].OpeningDate)