Add clusterEnabled to Options

Hello,

Thank you for this awesome library. 

When I use it in my app, some of the points are very near to each other, so when user clicks on the cluster, the cluster does not expand to individual pins. 

So I add an option to disable clustering. In my app, whenever zoom exceed some certain level, I just disable clustering so user can access individual pins.

```java
	@Override
	public void onClusteringStarted() {
		if (map == null) {
			return;
		}
		if (map.getCameraPosition().zoom >= 15) {
			options.setClusterEnabled(false);
		} else {
			options.setClusterEnabled(true);
		}
	}
```