Make Changes for adding and firing events

There are two problems which I faced:

```
$ready = new \Khill\Lavacharts\Events\Ready('readyCallBack');

$linechart->events([$ready]);
```
This was throwing an error because of namespacing problem. `is_subclass_of($event, '\Lavacharts\Events\Event')` returns false.

2nd Problem:

Registering for events like 'ready' show be done before calling draw. So I have just shifted the position to before draw during render.