Cleaning up our themes folder

To have a much more manageable theme folder, let's take a few moments to do some housecleaning. First, let's set the Bartik theme back as our default. Once that is complete, we can uninstall Bootstrap 3, ZURB Foundation, and Neato themes. Finally, once the three themes are uninstalled, we can remove them from our themes folder as we will not be using them anymore.