Switch Vim back to Solarized colorscheme (again)

Since the Solarized theme was included in iTerm recently, the setup is now quite
pain free.

If you name your Solarized profiles "light" and "dark" in iTerm, the Vim theme
will auto magically match the currently used flavor in iTerm.
Enable trackpad scrolling in normal mode in Vim (requires iTerm)
Add vim-fugitive as submodule