Feature/enhancement image embeds

The <img>tag which has already existed was also added to the object of interactive.
I see, and I was misunderstanding that.
by the way, I do not want to include `<div class="mediumInsert">` in the data returned by serialize. 
Because they are not used at the display of data.
How is it an idea about it?

example: 

```
<div class="mediumInsert" id="mediumInsert-4">
  <figure class="mediumInsert-images">
    <img src="http://*********.jpg" alt="">
  </figure>
</div>
```

to 


```
<div>
  <figure><img src="http://*********.jpg" alt=""></figure>
</div>
```