[WIP] Adding assert for type and tag

Implements `assertWrappedElement` to check for correct wrapped element in typified elements.

Closes #53 
I think that single array where mix of `tag name` to `allowed attributes` would be more flexible. For example:

```php
array(
    array('tag' => 'input', 'attrs' => array('type' => 'checkbox|radio')),
    array('tag' => 'select', 'attrs' => array('class' => '*')),
)
```

If array is empty we exit the `assertWrappedElement`. Then we cycle through array and if `tagName` matches tag of the element we look at `attrs` array. If that is not defined or is empty, then we continue to next allowed tag. We should record every positive match along the way and at the end of element cycle we check if at least one was matched. If none was matched then it's also an exception.