title: Rails remove old models with migrations
body: <p>I have a bunch of rails models that I'm re-writing into a single model to simplify my code and reduce unnecessary tables.</p>
  <p>I'm wondering what the best way to delete a model class and its table is.  I want past migrations to still succeed, but I don't want to leave the empty models lying around.</p>
  <p>Do I have to manually delete the old migrations that reference these models, then manually delete the class files?</p>
  <p>Does anyone have any tips for the best way to do this?</p>