Vim: prefer Python 3 for gundo
Vim: prefer Python 3 for gundo

On my sandbox, I was only able to get Python 3 to work. With this
setting, gundo works there, and it continues to work on my OS X box too
(which only has Python 2 support).

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

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