Add skip option

[gsvr]

There should be an optional 'Skip' option that can be activated for the LocationState that allows a user to not choose a location but move on from the LocationState. So the footer would look something like: n. Next b. Back s. Skip See https://github.com/praekelt/go-jsbox-location/commit/b79bea9ea5509689a406abc54fabb5c721cc74fd for an example.

[hodgestar]

This would involve:

• Adding a skip_text option that defaults to null.
• If skip_text is not null, display a skip option.
• If skip is selected, call self.next with null.