Update emailusernames/utils.py

Actually migrate the username.
Update emailusernames/backends.py

Allow for 'username' explicitly in the authenticate() method. Some authenticators (like tastypie's) expect to authenticate() using 'username'.
Update emailusernames/tests.py

Woops. Test for new behavior.
Merge pull request #44 from urbanape/patch-1

Update emailusernames/utils.py
Version 1.6.4
Use kwargs to keep backwards compatibility with authenticators that expect positional args.
utils.py: _DUPLICATE_USERNAME_ERRORS matches beginning of IntegrityErrors.

PostgreSQL 9.1 now spits out more descriptive errors, so we should move
to an re match instead of a simple string match.
Fix login template implementation.
Merge pull request #47 from jnns/patch-2

Fix templatetag compatibility with Django 1.5
Merge pull request #49 from ecometrica/django-tests

utils.py: _DUPLICATE_USERNAME_ERRORS matches beginning of IntegrityErrors
Update README
Merge https://github.com/urbanape/django-email-as-username
Fixes to @urbanape's fix for EmailAuthBackend.authenticate().

See pull request #45.