Doc fix in passage about Overriding Properties

[Former user]

In the code under http://www.sqlalchemy.org/docs_03/adv_datamapping.myt#advdatamapping_properties_overriding

In the line

def _get_email(self, email):

the email parameter must be removed. After the line

'_email': mytable.c.email

a comma is missing.

[Mike Bayer]

changeset:2225