Fixed unit test with optional url parts in #22

There is a unit test which is failing because the `.` character is not recognized as a valid part separator. This pull request addresses the issue and allows the following assertion to hold:

    $this->router->map('GET', '/bar/[:controller]/[:action].[:type]?', 'bar_action', 'bar_route');
    $this->router->match('/bar/test/do.json', 'GET')) ===  array(
	'target' => 'bar_action',
	'params' => array(
		'controller' => 'test',
		'action' => 'do',
		'type' => 'json'
	),
	'name' => 'bar_route'
    )

None of the other unit tests were broken.