Material工具栏组件toolbar

用途：一般用于头部或标题栏。通过<md-toolbar-row>支持多行，内部布局是基于flex的。

<md-toolbar color="primary">
  <span class="fill-remaining-space"></span>
  <span>&copy;接回的电子产品</span>
  <span class="fill-remaining-space"></span>
  <md-toolbar-row color="primary">
    <span class="fill-remaining-space"></span>
    <span>第二行</span>
    <span class="fill-remaining-space"></span>
  </md-toolbar-row>
  <md-toolbar-row color="primary">
    <span class="fill-remaining-space"></span>
    <span>第三行</span>
    <span class="fill-remaining-space"></span>
  </md-toolbar-row>
</md-toolbar>