Remove unused submodules directories.

Running `rake install`, runs the `:submodule_init` task,
which in turn runs the following command:

    git submodule update --init --recursive

This fails with the following couple of errors (separately):

    No submodule mapping found in .gitmodules for path 'vim/bundle/mattn-zencoding-vim'
    No submodule mapping found in .gitmodules for path 'vim/bundle/skwp-vim-indexed-search'

This was introduced by 3d60f721dd53e7f5414d11004c749784efc74f64
which removed the 'mattn/zencoding-vim' and 'skwp/vim-indexed-search'
submodules from the `.gitmodules`.
Merge pull request #243 from gonzedge/submodules-init

Remove unused submodules directories.
Vim plugins and prezto updated
Improved sass colors
Remove arpeggio; unused
Added vim-gitgutter, which shows git diff in the gutter
Upgrade plugins
Merge pull request #246 from irrationalfab/vim-gitgutter

Added vim-gitgutter, which shows git diff in the gutter
Upgrade plugins
Remove gitgutter; causes errors
Merge remote-tracking branch 'upstream/master' into customizations

* upstream/master:
  Remove gitgutter; causes errors
  Upgrade plugins
  Upgrade plugins
  Added vim-gitgutter, which shows git diff in the gutter
  Remove arpeggio; unused
  Improved sass colors
  Vim plugins and prezto updated
  Remove unused submodules directories.