The diffs in here are a little confusing. This `.modal-bar-hide` class was basically split into two separate classes: `.popout`, which just removes the ModalBar from the flow, and `.offscreen`, which translates it offscreen and animates it. These were then moved into the `.modal-bar` rule as nested selectors.

Note that the only reason this was called `.modal-bar-hide` instead of just `hide` was that it was conflicting with a Bootstrap class of the same name. To avoid that I just renamed the hidden state `.offscreen`, which doesn't seem to conflict with anything.