Merge pull request #22 from sangheestyle/master

remove unused import in example

Author: syrusakbary

README.md

@@ -22,7 +22,7 @@ Here is a simple SQLAlchemy model:
 
 ```python
 from sqlalchemy import Column, Integer, String
-from sqlalchemy.orm import backref, relationship
+from sqlalchemy.orm import relationship
 
 from sqlalchemy.ext.declarative import declarative_base