Missing url slash at Router::url() in 3.0

I don't speak much English.

## Problem

Example : 
<?= $this->Form->create(null, array('controller' => 'Menus')); ?>
<?= $this->Form->create(null, array('url' => '/Menus')); ?>
 
output is:
<form action="/cakephpMenus" ...

That must be :
<form action="/cakephp/Menus" ...

## Solution
Because String argument test does not exist in "Router::url()",
I add two assertEquals().

## comment
I run test "Router" and it is success. And I run all tests.
Since I do not understand specification well, I have a possibility of being wrong.