ImageViewer 图片查看器 不使用show.sync，改用v-model

[zlab]

mand-mobile version/项目版本
1.0.7

expectant behaviors/期待行为

<md-image-viewer
      v-model="showViewer"
      :list="imageList"
      :has-dots="true"
      :initial-index="viewerIndex">
    </md-image-viewer>

actual behaviors/实际行为

<md-image-viewer
      :show.sync="showViewer"
      :list="imageList"
      :has-dots="true"
      :initial-index="viewerIndex">
    </md-image-viewer>