In _parseString(), including . (dot) character in the regex pattern, for matching "compact syntax" paths with shorthand library notation

Prior to this update, library dot notation does not work when using compact URL syntax. For example,

$url = Router::match(array('myplugin.Posts::view', 'id' => '1138'));

fails because the . character is unrecognized within _parseString(). By including the . character in the regex pattern, the above compact URL path will be parsed; the controller portion, "myplugin.Posts" will subsequently be parsed by _parseController(), which handles the "myplugin" library component.