Big release

Huge internal refactor to use the new final API of Ember Basic Dropdown internally, to make it more flexible and easy to customize.

The public API of the component remains the same with the exception that trigger no longer needs a wrapper div, so the main component is tagless and the class attribute has no effect on it. The component can still have a tag and a class if the user passes tagName="div" class="whatever", but that is not the default anymore. Some classes have changed to make the css hierarchy flatter. That won't affect you unless you are customizing the default styles by targeting that specific class.

There is more work to be done in the 0.11 series:

• Remove hacks needed prior to 2.3 in inputs.
• Use ember-concurrecy to simplify internals.
• Thanks to the new flexibility of Ember Basic Dropdown, the multiple select can be simplified