issue #400 comment time conversion to local timezone

Fixed problem where comment times where not being translated from GMT to local
timezone.

Before:
```
function comment_time() {
  if($time = Registry::prop('comment', 'date')) {
    return strtotime($time);
  }
}
```
After:
```
function comment_time() {
  if($time = Registry::prop('comment', 'date')) {
    return Date::format($time,'U');
  }
}
```