four-of-a-kind is missing in highestRank()

[vasyl-shumskyi]

Looks like four-of-a-kind is missing in the highestRank() function

var highestRank = function (hand) {
    var result = "bust"; // default is bust

    if (containsRoyalFlush(hand)) {
        result = "royal flush";
    } else if (containsStraightFlush(hand)) {
        result = "straight flush";
    } else if (containsFullHouse(hand)) {
        result = "full house";
    } else if (containsFlush(hand)) {
        result = "flush";
    } else if (containsStraight(hand)) {
        result = "straight";
    } else if (containsThreeOfAKind(hand)) {
        result = "three of a kind";
    } else if (containsTwoPair(hand)) {
        result = "two pair";
    } else if (containsPair(hand)) {
        result = "pair";
    }

    return result;
}