Fix documentation on the default queue for start_queue

[fanzeyi]

See #105

honeydew/lib/honeydew/queues.ex

Lines 30 to 36 in 1b07343

	def start_queue(name, opts) do
	{module, args} =
	case opts[:queue] do
	nil -> {Mnesia, [ram_copies: [node()]]}
	module when is_atom(module) -> {module, []}
	{module, args} -> {module, args}
	end

The default queue is Honeydew.Queue.Mnesia.

[koudelka]

thanks!