Displays info about [un]installed versions

Displays version when installing and uninstalling -- e.g.:

    Successfully installed pyrepl-0.8.4 pytest-2.6.4

and:

    Uninstalling pyrepl-0.8.4:
      Successfully uninstalled pyrepl-0.8.4
    Uninstalling pytest-2.6.4:
      Successfully uninstalled pytest-2.6.4