Make the config dict mutable so sqla writes it properly

hiboo/models.py

 from passlib import context, hash
 from flask import current_app as app
-from sqlalchemy.ext import declarative
+from sqlalchemy.ext import declarative, mutable
 from datetime import datetime
 from flask_babel import lazy_gettext as _
 
@@ -57,6 +57,7 @@ class Base(flask_sqlalchemy.Model):
 db = flask_sqlalchemy.SQLAlchemy(model_class=Base)
 
 
+@mutable.MutableDict.as_mutable
 class JSONEncoded(db.TypeDecorator):
     """ Represents an immutable structure as a json-encoded string.
     """