Copy over data attrs from video el to wrapper el.

We should be mimicking the video element more closely, so, the wrapper el should not be losing any of the data-attributes that were added before the creation of a player.
You could use vjs.obj.each here. But also, you could move the div creation down to here and do `vjs.Component.prototype.createEl.call(this, 'div', attrs)`. 

And there's nothing special about component.createEl, so you could just do vjs.createEl() there if you wanted to simplify that. Component.createEl should actually probably set this.el_ after creating. But don't worry about that for this.