fix issue #455

[leonardoo]

in python 3 all model must be have the str method because unicode doesn't exist

https://docs.djangoproject.com/en/1.7/topics/python3/#str-and-unicode-methods

[coveralls]

Coverage increased (+0.03%) to 95.27% when pulling e2a52f1 on leonardoo:master into b398e07 on bread-and-pepper:master.

[coveralls]

Coverage increased (+0.34%) to 95.58% when pulling 1e506be on leonardoo:master into b398e07 on bread-and-pepper:master.

[swistakm]

Great. I saw that you have simplified code for emails so I will need to take closer look on that. I will try to review it as soon as possible.

[leonardoo]

please close this pull, i will split it in two pulls