Updated the migrations to support 1.5 custom user models.

- Fixes being unable to run the migrations to setup fluent_pages in an existing 1.5 project with custom user model.
Fixed some specificity stuff.

- added user_model_label to the __all__ definition
- corrected the import statements to correctly call from utils.compat
Merge pull request #27 from techdragon/master

Fix 1.5 Custom User Model support in Migrations