Now uses billiard.py2 and billiard.py3 packages so that the version specific modules are not handled by setup.py.  Closes #105
Fixes "cannot join process not started" error
Bumps version to 3.3.0.15 and updates CHANGES.txt
Make sure billiard.py3 is included in MANIFEST
Bumps version to 3.3.0.16 and updates Changes