vim: vundle: add vim-unimpaired
git: v2.1

The default value we give to the environment variable LESS has been
changed from "FRSX" to "FRX", losing "S" (chop long lines instead of
wrapping). Override the new default only for "git blame".

The "core.preloadindex" configuration variable is enabled by default,
allowing modern platforms to take advantage of their multiple cores.