docco-resize.js added

Hi, to use this script, you need to add the following css:
```css
div.handler{
      width: 5px;
      padding: 0;
      cursor: col-resize;
      background: red;
      position: absolute;
      z-index: 5;
}
```
And remove the restriction `width: 50%;` to `td.code`.
Thank you!