Fix command line extension wizard issues
Created by: msmolens
Fix issues using the command line extension wizard on Windows found when checking the status of http://na-mic.org/Mantis/view.php?id=4182.
Note that the AttributeError and path interpretation problems discussed in the bug are no longer issues with the latest Slicer and Git for Windows that reports the following version:
$ git --version
git version 2.12.2.windows.2