little tool for tournament cross-tables
ordered_keys = function(t)
	local result = {}
	local s = {}
	for team in pairs(t) do
		table.insert(result, team)
		s[team] = score(t, team)
	end
	table.sort(result, function(t1, t2) return s[t1] > s[t2] end)
	return result
end