fix(gmap-vue): change repaint method by render

We change the repaint method to render and use markers property instead
of the old method getMarkers.
The setMap methos is inherited from OverlayView class.

Fix #247

packages/gmap-vue/src/components/cluster-icon.vue

@@ -109,12 +109,12 @@ export default {
   },
   updated() {
     if (this.$clusterObject) {
-      this.$clusterObject.repaint();
+      this.$clusterObject.render();
     }
   },
   methods: {
     reinsertMarkers() {
-      const oldMarkers = this.$clusterObject.getMarkers();
+      const oldMarkers = [...this.$clusterObject.markers];
       this.$clusterObject.clearMarkers();
       this.$clusterObject.addMarkers(oldMarkers);
     },