title: Runtime changing model with mongodb/mongoid
body: <p>I've to add several fields in a mongoid model, I know there is not migration with MongoDB but if I go on without dropping the DB, making rails to "regenerate" the DB entirely, it doesn't display or use the new fields at all ! </p>
  
  <p>What's the best way to go here ? Is there something softer than drop/reopen mongodb ?</p>
  
  <p>Thanks in advance
  luca</p>