2019-05-31：逐步理解小程序的UI设计

<view class='spacing' style='height:100rpx'>
  <view class='weui-flex' style='height:50rpx'>
    <view class='weui-flex_item' style='height: 100rpx'>
      <progress style='color: red' percent='30' style='height:100rpx'>
      </progress>
    </view>
  </view>
</view>
<view class='weui-cells'>
  <view class='weui-cell weui-cell_switch'>
    <view class='weui-cell_bd'>show percentage</view>
    <view class='weui-cell_ft'>
      <switch data-name='showInfo' checked='{{showInfo}}' bindchange='onSwitchChange'>
      </switch>
    </view>
  </view>
</view>