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.