Adding class to the datepicker

I'm using the content-class prop to add a custom class to the datepicker calendar but its not showing in my app.

```
 <VueDatePicker
   content-class="task-date-picker"
    v-model="modalData.item.due_at"  >
</VueDatePicker> 
```

And the output is shown below:

https://capture.dropbox.com/KAYcJNMorQhTF7H4?src=ss

Am I missing something here?

