Extends spin.js to show an image inside the spinner. Uses an <img> node.

Example of usage:

> opts = {
>		innerImage: {
>			url: 'img/logo.png', /* relative path from HTML site point of view */
>			width: 58, /* width of <img> node */
>			height: 58 /* height of <img> node */
>		},
>		lines: ….