[Feature request] Give "switch instantly" the same functionality to cycle through sequentially older tabs

[cbadams2]

I love this extension and think you all have done a great job with it! I was wondering if it was possible, with the "switch instantly" shortcut (I think Alt+z by default), to cycle through sequentially older tabs? Right now, if you hold hit Alt+z, hold the Alt key, and then press z again, it will just switch back and forth between the same two tabs. I was wondering if it would be possible to give it the same behavior as with the alt-tab-style popup menu (where Alt+z+z would take you to your second most recently used tab, and so on), just without the popup. I think this would be a really advantageous feature because the instant switching is quite a bit faster than with the popup (on my system, at least), and most of the time when I'm switching tabs, I don't need to see the info of the tab I'm switching to.