consistent event for shape creation

Hi,
Thanks a lot for this quality plugin ; ) 

This request would allow a more consistent scheme for event handling once a shape is created. 

For instance, in the example file, instead of having 4 handling functions for each shape created like:
```js
var drawnItems = new L.LayerGroup();
		map.on('draw:poly-created', function (e) {
			drawnItems.addLayer(e.poly);
		});
		map.on('draw:rectangle-created', function (e) {
			drawnItems.addLayer(e.rect);
		});
		map.on('draw:circle-created', function (e) {
			drawnItems.addLayer(e.circ);
		});
		map.on('draw:marker-created', function (e) {
			e.marker.bindPopup('A popup!');
			drawnItems.addLayer(e.marker);
		});
```

you could jus use: 

```js
map.on('draw:created', function (e) { // e being an object {shape: theShape, type: its type}
                       if(e.type == 'maker') {
                           e.shape.bindPopup('A popup!');
                           }
		       drawnItems.addLayer(e.shape);
		});

```
cheers, 
C.