Add .vundles.local to allow per-installation plugin customization

Adding and removing vim plugins is now done by adding and removing
from ~/.vim/.vundles.local. This file is sourced at the end of
vundles.vim

Fixes #275

.gitignore

@@ -7,6 +7,7 @@ vim/.netrwhist
 vim/tmp
 vim/spell
 vim/after/.vimrc.after
+vim/.vundles.local
 vim/bundle
 .netrwhist
 bin/subl