use custom user model
fix user imports
make compatible with 1.4
put settings back
Fix circular dependencies around custom model
Migration uses custom model

This is not completely correct as there is still an embedded copy of
the auth.User model inside the migration, but it should work well enough
for most purposes.

Thanks to AJ Bahnken
Merge pull request #105 from mixcloud/mc_custom_user_model

Django 1.5 custom user model