pressing space while the modal is up scrolls the content behind the modal

[ggerard]

Not sure if this is expected behavior but seems wrong for a modal.

In the demos, say the first translucent demo, the modal pops up, behind the modal is grayed over.

I press space and the demo page scrolls behind it.

[lukemelia]

@ggerard There's nothing currently in ember-modal-dialog that captures focus. It would be great to document how to do this and possibly to add something to the library to assist with this.