element-el-table、el-pagination，实现自动编号

1.默认排序

   <el-table-column type="index" label="序号" align="center" width="60">
   </el-table-column>

2.实际所需排序

    <el-table-column type="index" label="序号" align="center" width="60">
      <template scope="scope">
        <span>
          {{ (currentPage - 1 )* pageSize + scope.$index + 1}}
        </span>
      </template>
    </el-table-column>