Add click listener into checkbox directive to bind value

Ignition order of `click` event and `change` event is dependent on implementation of browsers.

For example;

- Google Chrome:   `change` -> `click`
- Mozilla Firefox: `click` -> `change`

If `click` event is used on Firefox with `v-on` of current vue.js, it cannot use bound value by click.
So added click listener.

Could you review this?