Vim: disable folding when viewing diffs
Vim: disable folding when viewing diffs

This sometimes happens when doing things like `e` in a `git add --patch`
run; you get dropped into an editor and have a bunch of unwelcome folds
that you end up getting rid of immediately.

Signed-off-by: Wincent Colaiuta <c76ac2e9cd86441713c7dfae92c451f3e6d17fdc@wincent.com>

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent