Guess we should send an email to user on any failed checker.

[akshar-raaj]

https://github.com/agiliq/django-secure-login/blob/master/secure_login/backends.py#L34

Currently an email will be sent in case of wrong username and password combination. But if a checker fails, an email will not be sent, becuase authenticate returns as soon as a checker fails.
https://github.com/agiliq/django-secure-login/blob/master/secure_login/backends.py#L30

I guess we want to notify the user when a checker fails.