调整element-ui中多个button处于同一行

参考：

https://element.eleme.cn/#/zh-CN/component/dropdown

    <el-row>
      <el-button-group style="margin-bottom:20px">
        <el-button size="small" type="primary" icon="el-icon-plus"></el-button>
        <el-button size="small" type="primary" icon="el-icon-edit"></el-button>
        <el-button size="small" type="primary" icon="el-icon-delete"></el-button>
      </el-button-group>
      <el-dropdown trigger="click">
        <el-button size="small" icon="el-icon-s-grid">
          <i class="el-icon-arrow-down el-icon--right"></i>
        </el-button>
        <el-dropdown-menu slot="dropdown">
          <el-dropdown-item>黄金糕</el-dropdown-item>
          <el-dropdown-item>狮子头</el-dropdown-item>
          <el-dropdown-item>螺蛳粉</el-dropdown-item>
          <el-dropdown-item>双皮奶</el-dropdown-item>
          <el-dropdown-item>蚵仔煎</el-dropdown-item>
        </el-dropdown-menu>
      </el-dropdown>
    </el-row>

css：

.el-dropdown {
  vertical-align: top;
}