UI for additional login methods

[audiodude]

If we are to support additional login methods (#36), we need some kind of UI for displaying them on the homepage. Many sites I see simply use a "stacked pill" style interface, where the login methods are simply shown one after another with each of the "login pills" stacked on top of each other. This would presumably be fine, but gets complicated if we also show a email token (#35) authentication method.