Change to use jQuery Terminal's mousewheel event handler

Even event receiver was missing in mousewheel event hander that was in try-groonga.js at 2ad0518a43a45983166780456fd371563b089b78, terminal
seemed to respond to mousewheel event.

I investigated why and it turns out that:

```
All interpreters have attached mousewheel event so you can stroll them
using mouse.
```
"Additional terminal controls" in [API Reference](http://terminal.jcubic.pl/api_reference.php)

So, all you need to handle mousewheel event in jQuery Terminal is just including jQuery Mouse Wheel plugin.