Add ability to reinstall a Python version

Fixes #60
Add support for Stackless 3.2.5 and 3.3.5

Applied this patch on OSX  to fix compilation:
http://hg.python.org/stackless/rev/5260e681195d
Merge branch 'dev'

Conflicts:
	pythonz/installer/pythoninstaller.py
Add reinstall option to bash completion
Raised version and updated changelog