======================================================================
Enhancements to installation script: ``--version`` and ``--uninstall``
======================================================================


Use case
--------

User might wish to control which rally version is installed or even purge
rally from the machine completely.


Problem description
-------------------

    #. Installation script doesn't allow to choose version.
    #. No un-install support.



Possible solution
-----------------

    #. Add ``--version`` option to installation script.
    #. Add ``--uninstall`` option to installation script or create an
       un-installation script
