xmonad: Enable three more usable windows

Signed-off-by: Lance Chen <cyen0312@gmail.com>
xmonad: fix dmenu binding

Signed-off-by: Lance Chen <cyen0312@gmail.com>
vim: Add latex plugin

Signed-off-by: Lance Chen <cyen0312@gmail.com>
vim: Reduce foldcolumn level

Signed-off-by: Lance Chen <cyen0312@gmail.com>
vim: highlight border on column 80

Signed-off-by: Lance Chen <cyen0312@gmail.com>