Increase OrganizationAddForm email max_length to 75

In keeping with email field length in OrganizationUserAddForm
Merge pull request #20 from philmcmahon/master

Increase emailfield length to 75 for OrganizationAddForm
Adds `get_or_add_user` to Organization user

Adds `get_or_create` functionality for users on Organiation class.
Replace auth.User references in migrations

Supports swappable user models.

Closes gh-19
Test against Django 1.5
Escapes org and user names in default templates
stop context object in _send_email autoescaping
Merge pull request #21 from philmcmahon/email-html

stop context object in _send_email autoescaping
Add Python 3.2 to Travis
Update for new patch version
Clean up docstrings
Documentation update (backends)
Reorg the docs
Adds reference outlines, version bump
Exclude Django<1.5 from Python 3.x

If ever Travis-CI will dedupe this repo from my account, this will be able to
run from the primary repository.
Add title formatting to docs title
Update repo URL
Include Django 1.6 beta for testing
Try fixing matrix exclusions

Only test with Django 1.4 on Python 2.x and only test with Django 1.6b on
Python 2.7.x and above.
Use str representation for Python3 compatability