modifierReplace : implode modifier 

I had an error when I did the following:

```php
 $t = new Tpl;
 $t->assign('arraytest',array('this', 'is', 'a', 'test');
 $t->draw('test');
```

In the test template I tried to implode the array with a whitespace:
```html
{$arraytest|implode:" "}
```

But the result threw an error
```
Parse error: syntax error, unexpected ';'.......
```
 
Expected result:
```
this is a test
```

So I added and \s to the preg_match on line 610 of the Parser.php file.


Barry