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
Merge remote-tracking branch 'upstream/master'