Add Vim key bindings to use instead of just arrow keys

First of all, let me just say, im really enjoying this repo, great job!

I am a big vim user and I know that other terminal users that use vim would LOVE to have vim key bindings for the up, down, left and right (h,j,k,l) instead of just the arrow keys.

So if its ok ill go ahead and make a PR for exactly that and add the option to use the vim key binding keys aswell