Setting bufhidden=hide in vimrc

This is particularily valuable for various scripts that perform manipulation
on buffers, as unloading a buffer not only requires saving, but discards
modification history for undos.

vimrc

@@ -28,6 +28,7 @@ set ai
 set autochdir
 set backspace=indent,eol,start
 set backupdir=~/.vim-tmp,~/.tmp,~/tmp,/var/tmp,/tmp
+set bufhidden=hide
 set directory=~/.vim-tmp,~/.tmp,~/tmp,/var/tmp,/tmp
 set et
 set exrc