Add scroll bars back into tabs but at the price of removing zooming.

* Remove zoom UI because it doesn't appear to work with a scrolled tab
  and I've spent many previous hours trying to figure out why. Provide
  error messages when trying to zoom
* It looks as if scrolling is the more important feature as described in
  #69
* It looks as if these two functionalities work with JavaFX as explained
  in #68