Update filter logic to use new embed template and embed API endpoints

@anthonyt Want to have a look through this?
Just noticed that this is now the only get() call we're making ... if we just replace it with

```php
$html = "<iframe src=\"URL\" mozallowfullscreen=\"mozallowfullscreen\" webkitallowfullscreen=\"webkitallowfullscreen\" width=\"WIDTH\" allowfullscreen=\"allowfullscreen\" height=\"HEIGHT\" scrolling=\"no\" frameborder=\"0\"><\/iframe>";
return $html;
```

then there's no API interaction at render time at all, removing lag and potential for error