Installer: better warnings for submodules that have been deleted

[skwp]

Here's an example from someone who had a bunch of local bundles that were not supposed to be part of yadr any more. We removed them from submodules but the dirs still hang around. The installer script should warn in this case and provide a command for user to run ("git clean -df" should probably do it)

~yadr master ✗ ➤ git status
# On branch master
# Your branch is ahead of 'origin/master' by 54 commits.
#
# Untracked files:
#   vim/bundle/garbas-vim-showmarks/
#   vim/bundle/joestelmach-javaScriptLint/
#   vim/bundle/kien-tabman/
#   vim/bundle/mikefarmer-snipmate/
#   vim/bundle/rson-vim-conque/
#   vim/bundle/skwp-vim-rspec/
#   vim/bundle/vim-scripts-taglist/
#   vim/snippets/
#   vim/vim
nothing added to commit but untracked files present

See also #63

[kylewest]

git clean doesn't work for me. does it work for you?

[skwp]

yeah i think something is up with cleaning and submodules :/ i didn't have time to look into it yet

[taybin]

I use git clean -fxd