Simple readme update.
Add status button to readme
Email Model.
EmailType model.
Unsubscribed model
Some model documentation
Corrected FK references.
fixed incorrect reference in docstring.
EmailType.name should be unique.
Subentity specified by nullable FK to ContentType.
Merge pull request #1 from Wilduck/models

Models
Immediate email signal handler outline.
Resovle circular import by moving import statement
Test and install requirements and installed_apps update.
Signal Handling tests, plus spelling/sematic corrections.
Removed dummy tests.
small doc update.
Added Email.subject field.
Celery email task outline.
Test tasks.get_email_addresses handles subentites.