Handle overflow in Term::move_backward
Handle overflow in Term::move_backward

Resolves #25

dannydulai/alacritty,alacritty/alacritty,jwilm/alacritty,jwilm/alacritty,dannydulai/alacritty,jwilm/alacritty,jwilm/alacritty,alacritty/alacritty