Add SQLAlchemy configuration to avoid warning.

accountant/__init__.py

@@ -28,6 +28,7 @@ app.config.from_pyfile('config.cfg')
 
 app.config['SQLALCHEMY_ECHO'] = app.debug
 app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True
+app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True
 
 # Database initialization.
 db = SQLAlchemy(app)