Added WIP (work in progress) feature to git.plugin

Allow with 2 shortcuts ('gwip' and 'gunwip') to create a temporary commit to switch to another branch and keep working normally before coming back and continue your work.
A notification function has also been added to return the branch status: 'WIP!!!' if your current branch is a wip.

Because I am using the 'gallois' theme, I have updated it to integrate the wip notification.

*Tested on a Mac using iTerm2