Adding a spinner to the Future theme

@zackbloom starting this PR off. After you add the on/off classes (`message-spinner-active`, `retrying-soon`, `retrying-later`, or whatever you decide), let me know because there are a couple bugs I'll need to clean up at that time. (Believe it or not, the alert orb is changing its size when the spinner is toggled, so I'll need to adjust accordingly in the activated class. There are also a few minor tweaks still left to be made but it will make more sense to make those after the coffee is fleshed out.)