Fixed the EventDispatcher, listening to Restler events is now possible in the following ways

```php
<?php //index.php

//adding event listeners with the class
Restler::addListener('onCall',function(){
    echo "Restler::addListener('onCall')\n";
});

$r = new Restler();

//adding event listeners with the instance
$r->addListener('onGet',function(){
    echo "\$r->addListener('onGet')\n";
});

//calling the event method
$r->onNegotiate(function(){
    echo "\$r->onNegotiate()\n";
});

//bulk listening
$r->on(array(
    'call' =>function(){
        echo "on call\n";
    },
    'get' =>function(){
        echo "on get\n";
    },
));
$r->addAPIClass('Say');
$r->handle();
```

above code on the hello world example gives

    $r->addListener('onGet')
    on get
    $r->onNegotiate()
    Restler::addListener('onCall')
    on call
    "Hello world!"

Fixes #186