Styling clusters about js-marker-clusterer

[Remo]

@ivanproskuryakov do you mind creating this PR against our fork at https://github.com/gmaps-marker-clusterer/gmaps-marker-clusterer? This repo isn't maintained anymore. Could you also elaborate what problems we get without clusteringbegin and clusteringend?

[ivanproskuryakov]

@Remo

do you mind creating this PR against our fork at https://github.com/gmaps-marker-clusterer/gmaps-marker-clusterer?
Sure, will do that

Could you also elaborate what problems we get without clusteringbegin and clusteringend?

This will give possibility to handle events for visible set of clusters only, ex: better performance

// Adding preloading for visible clusters 
    MapPropertyCollection.prototype.bindClusterEvents = function () {
        var _this = this;

        google.maps.event.addListener(this.cluster, 'clusteringend', function () {
            _this.preloadPreviews();
        });
    };

// And later, show cached image on mouse over
    google.maps.event.addListener(marker, 'mouseover', function () {
         infoWindow.open(_this.map, this);
         _this.showPreview(marker);
    });