yyzone/src/components/base/button/button-group.md

yyzone vue components and utils

```vue
    import Vue from 'vue'
    import YYButtonGroup from './button-group'
    import YYButton from './button'

    Vue.component('YYButtonGroup', YYButtonGroup)
    Vue.component('YYButton', YYButton)

    <YYButtonGroup>
        <YYButton type="default">Primary</YYButton>
        <YYButton type="ghost" theme="dark">Ghost</YYButton>
        <YYButton type="ghost" theme="dark">Ghost</YYButton>
    </YYButtonGroup>
```