code: public static CurrencyPair fromLunoPair(String lunoPair) {
      return new CurrencyPair(
          fromLunoCurrency(lunoPair.substring(0, 3)), fromLunoCurrency(lunoPair.substring(3)));
    }
docs: convert luno pair to xchange pair i.e. XBTZAR -> BTC/ZAR we assume, the pair has two currencies
  with 3 chars length each <- not a very clean approach
  
  @param lunoPair
  @return