Feature/fix paper getbyid

Modified and fixed `paperproto.getById` so that element reference cab be retrieved from Raphael ID. Post this, codes like this will be possible.

```javascript
window.onload = function () {
	var p = window.paper = Raphael(document.getElementById('containerDiv'), 300, 300),
        g;

    g = p.group().click(function (e) {
        var target = p.getById(e.target.raphaelid);
        alert(['clicked on', target.type, target.id].join(' '));
    });

    p.rect({
        x: 10,
        y: 10,
        width: 100,
        height: 100,
        fill: '#ff0000'
    }, g);

    p.rect({
        x: 110,
        y: 110,
        width: 100,
        height: 100,
        fill: '#ff0000'
    }, g);

};
```