bgPreview and toggleItems

Added bgPreview and toggleItems options.

bgPreview: Instead of just displaying the main preview, allow it to change the background instead. (Does not require previewImage to be true)

toggleItems: toggle classes on specific items, great for only showing the upload button once item. 

```javascript
$('[type="file"]').ezdz({
		bgPreview:	'.backgroundPreview',
		toggleItems: {
			'.uploadButton': 'hidden',
			'.jumbotron':	 'transparent',
		},
	});
```