Keep "special" properties out of getDefaultProps

[job13er]

From a slack conversation:

FYI: Don’t put classNames in your getDefaultProps() of your component. It apparently breaks event bindings on the component itself (not it’s children) i.e. when you define a click() method or an Ember.on('click') for the component itself. I haven’t quite figured out why that is, and I’ve hit my limit of wanting to dig through ember innards today (2 hours was my max). For now, at least, I think we should not put the “special ember properties” in getDefaultProps() i.e. classNames tagName, classNameBindings, attributeBindings. I propose we put those above propTypes in our component definitions.

There are other reasons as well to avoid this. The concatenatedProperties functionality becomes broken when you use getDefaultProps() to set things like classNameBindings.