Update index.html

Apparently the **value** is being changed only, so we need to actually just set the callback to happen **on a value change** -- simple enough a fix:

```javascript
	myDataRef.on('value', function(snapshot) {
        var thedoorvalue = snapshot.val().doorvalue;
	$('#DoorValueDiv').html(thedoorvalue);
      });
```


I will also have to show you some jquery to change the text on a page:

```javascript
	$('#DoorValueDiv').html(thedoorvalue);
```

That line places our 'doorvalue' inside the part of our page that says ` <div id="DoorValueDiv"></div>` (the doorvalue plops right in the middle).