make md-collapsible actionable

[foxnewsnetwork]

As per this issue:
#112

now, md-collapsible can be made to split out an action when a user interacts with it:

{{#md-card-collapsible id="action-selection"}}
  {{#md-collapsible icon="mdi-image-filter-drama" title="Cloud" action="clicked" model="cloud"}}
    O misty eye of the mountain below
  {{/md-collapsible}}
  {{#md-collapsible icon="mdi-maps-place" title="Marker" action="clicked" model="marker"}}
    keep careful watch of my brothers' souls
  {{/md-collapsible}}
  {{#md-collapsible icon="mdi-social-whatshot" title="Fire" action="clicked" model="fire"}}
    and should the sky be filled with fire and smoke, keep watching over [indecipherable]
  {{/md-collapsible}}
{{/md-card-collapsible}}

If provided with action, it is now possible to handle this in your controller (or wherever):

export default Ember.Controller.extend({
  actions: {
    clicked(tabModel) {
      if(tabModel === this.get("activeSlide")) {
        this.set("activeSlide", null);
      } else {
        this.set("activeSlide", tabModel);
      }
    }
  }
});

If you passed in a model to the md-collapsible, it will be given to you as your first argument in your action handler. This way, you have some idea what model your user is trying to interact with.

[mike-north]

This looks great :) Thanks for your contribution