Fixes #19: Handle consecutive invalid chars in slugify

tests/CommonTest.php

@@ -333,6 +333,8 @@ abstract class CommonTest extends PHPUnit_Framework_TestCase
     {
         return array(
             array('foo-bar', ' foo  bar '),
+            array('foo-bar', 'foo -.-"-...bar'),
+            array('another-foo-bar', 'another..& foo -.-"-...bar'),
             array('foo-dbar', " Foo d'Bar "),
             array('a-string-with-dashes', 'A string-with-dashes'),
             array('using-strings-like-foo-bar', 'Using strings like fòô bàř'),