text: Title: Unable to add about_me and last_seen field in chapter 6 of The Flask Mega Tutorial.
  Body: Hello Miguel. Thank You for the tutorials. 
  
  I was following chapter 6. I created two new fields and executed 
  "flask db migrate -m "some text here" and "flask db upgrade"  commands. All was well.
  
  But when I restarted my server and reload my page. I got this error.
  
  ```
  sqlalchemy.exc.OperationalError
  
  sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such column: user.about_me
  [SQL: SELECT user.id AS user_id, user.username AS user_username, user.email AS user_email, user.password_hash AS user_password_hash, user.about_me AS user_about_me, user.last_seen AS user_last_seen 
  FROM user 
  WHERE user.username = ?
   LIMIT ? OFFSET ?]
  [parameters: ('idreamofghouls', 1, 0)]
  (Background on this error at: http://sqlalche.me/e/e3q8)
  ```
  
  And I seriously don't know how to counter it. I did "export FLASK_APP=appname" and "export FLASK_DEBUG=1" as well. 
  
  Please help me Miguel. I can't seem to find the solution anywhere and I'm still a beginner. 