fix typos

```shell
% python ./manage.py syncdb
lNFO 2014-11-07 21:02:16,035 base 1937 140735284790016 Raven is not configured (logging is disabled). Please see the documentation for more information.
CommandError: System check identified some issues:

ERRORS:
<class 'phoneconfirmation.admin.MessageTooLongAdmin'>: (admin.E108) The value of 'list_display[1]' refers to 'created', which is not a callable, an attribute of 'MessageTooLongAdmin', or an attribute or method on 'phoneconfirmation.MessageTooLong'.
<class 'phoneconfirmation.admin.MessageTooLongAdmin'>: (admin.E116) The value of 'list_filter[1]' refers to 'created', which does not refer to a Field.
<class 'phoneconfirmation.admin.SMSLogAdmin'>: (admin.E108) The value of 'list_display[4]' refers to 'created', which is not a callable, an attribute of 'SMSLogAdmin', or an attribute or method on 'phoneconfirmation.SMSLog'.
<class 'phoneconfirmation.admin.SMSLogAdmin'>: (admin.E116) The value of 'list_filter[1]' refers to 'created', which does not refer to a Field.
```