Enable to change buffer quickly on Vim

ref. http://kaworu.jpn.org/kaworu/2007-07-26-1.php
Use vim-auto-save

ref.
  http://qiita.com/kentaro/items/833075356d41e9d9bc75
  https://github.com/vim-scripts/vim-auto-save
Bundle configurations about auto saving
Disable auto saving after nothing is typed
Revert "Disable auto saving after nothing is typed"

This reverts commit 93b7b16c89e0cfa3664bfb95c5c04d77d4985293.
Merge branch 'vim-disable-auto-save-after-notype'