Merge branch 'master' of https://github.com/tangbc/vue-virtual-scroll-list

Author: tangbc

src/index.js

@@ -269,6 +269,7 @@ const VirtualList = Vue.component('virtual-list', {
         if (dataSource) {
           if (Object.prototype.hasOwnProperty.call(dataSource, dataKey)) {
             slots.push(h(Item, {
+              key: dataSource[dataKey],
               props: {
                 index,
                 tag: itemTag,