Added git stash completion options.

Squashed commit of the following:

commit 962a19dfab7f04552ce7919fff91e945bab53bde
Author: Mandeep Sandhu <mandeepsandhu.chd@gmail.com>
Date:   Wed Sep 18 18:09:49 2013 +0530

    Add missing 'git stash' completion options

    Fixed typo.

commit 57bbd89caf922228363418cacbfa1daeb352e520
Author: Mandeep Sandhu <mandeepsandhu.chd@gmail.com>
Date:   Wed Sep 18 17:59:36 2013 +0530

    Add missing 'git stash' completion options

    Added the following options which were missing:
    * save
    * branch