Remove Terminal.app

I've switched over to iTerm.app -- it seems to have much better support
for color schemes in Vim, amongst it's many other extra features -- so I
don't really see the need to keep around stuff related to an application
I'm no longer using.
Add command to update submodules

This command will perform a `git pull` for all submodules. It will also
do this for any submodules within submodules. The latter need to be set
up manually. There is currently only one, so I don't mind. If I have to
start adding more I'm sure I'll find a way to script this.