Dev 1.0 First Pull Request

please change method name to getAllByThread() and change this to static
```php
public static function getAllByThread($thread_id)
```
in L23 ~ 26
```php
$rows = $db->rows('SELECT * FROM comment WHERE thread_id = ? ORDER BY created', array($thread_id));
foreach ($rows as $row) {
    $comments[] = new self($row);
}
```