SelectEnhancer doesn't work with driver.execute_script('...', select)

When I do:

```py
driver.execute_script('alert(arguments[0].tagName)', page.select_element)
```

... it raises an exception:

    TypeError: <holmium.core.enhancers.SelectEnhancer object at 0x7f7af0ab44e0> is not JSON serializable

### Environment

* Python 3.4
* `holmium.core==0.8.5`
* `selenium==3.0.2`
* Firefox / Geckodriver