Add up/down arrows to reorder rankings

[brantonb]

Until drag & drop is implemented (#44), a useful stopgap could be up/down arrows for each team. There are arrows available in Bootstrap. The basic logic would be to swap the contents of the select/text elements with the ones above or below it, depending on the arrow that was clicked. If you want to move a team up 4 spots, you'd have to click the up arrow beside it 4 times as it moves up the list. Simple but straightforward.

[jdharms]

Made obsolete by implementation of drag and drop.

Arrows on mobile is something that might be explored in the (distant) future.