Using text-overflow property to hide content that overflow multi-select item container
Allowing MultiSelectView subclasses to redefine container and item tag names
Triggering a `render` event when MultiSelectView is rendered
Triggering a `move` event whenever an item is moved in MultiSelectView, either from available or selected lists.
Adjusting styles for multi-select
Making MultiSelect template more customizable

- Now you can pass a content template, so that the lists content wrapper tag can be redefined when rendering the template in Rails views.
- Allow one to add content for both selected and available actions container. In the available action container you add a content between the search and add all button. Its also possible to specify an option to the `render_multi_select` helper, instead of defining it in I18n file.
- Passing a `data` attribute to the `render_multi_select` helper will add data attributes to the main `multi-selet` tag.