Link multiple parties to multiple users #555

This patch creates a many to many relationship between party and nereid user.
This allows you to have any possibility of party-user relationship where a user
may switch current party to change parties. This also offers migration script
if the user had not installed the module and has existing users.
Allow test cases to run from setup.py

Since the suite was not returned from the tests module
python setup.py test command wouldn't run
Prepare release 2.4.0.1
Merge branch 'release/2.4.0.1'