Initial cut of abstract, extendable base models

The new metaclass allows for the creation of custom organization model
groups (organization, org user, org owner) that use their own tables and
can be modified by developers for their own project needs.
Clean up imports and add Django 1.7 app hook
Clean up the tox file & environment selection
Break up the new method on the metaclass
Fixes bad attribute reference
Use kwargs with `get_or_add_user`
Add a second fully custom orgs app to example

Oh what wonderous errors we have created.
Solves multi-module problem for metaclass

When base classes are used for models in multiple applications then it
is important to be able to separate those relationships.
Adds Jython environment

Not working yet due to virtualenv compatability problem
Move org user uniqueness constraint to base model

The unique constraint between a user and organization should be
maintained in every organization.
Add test custom models
Updates create_organization utility function

Still requires updates for handling old style arguments to maintain
backwards compatibility if feasible.
Consistent naming for internal variables
Adds initial cookbook docs
Updates examples documentation
Updates to the getting started section
Tests pass for Python 3 versions

At the expense of Django 1.4 for the time being. Ensure Django version
is at least 1.4.2 which is the first to include `six`. Requiring a
minimum minor version shouldn't impose any unnecessary challenges.
Add in workaround for Django 1.4 and six

Borrowed strategy from Django-polymorphism (thanks @vdboor!). Running
this with Django 1.4 the meta class is not switched out properly without
this workaround.

Refs:
https://github.com/chrisglass/django_polymorphic/blob/4be6d42fad60c3e97e4d37f3fc9125d623468908/polymorphic/base.py
Ignore complexity of __new__ method
Add support for Wheel packaging