Hi !

This plugin is great and fixes an unbelievable lack in Wordpress image alignment feature. But I don't understand why you use clearfix class and en-queue a whole style sheet when a basic inline style attribute would suffice. Furthermore your clearfix style sheet overlaps with Foundation, Bootstrap or Compass ones what I think is not desirable.
If you need something to target the divs in the code to replace them, perhaps just an empty clear-floats class would be sufficient ? And what the divider class is for ?

Nevertheless, great plugin ! 👍