Added 'configs' parameter for access to all CKEditor parameter settings

This will fix both #15 and #17 and provide essential access to all of the config parameters available with CKEditor!

Simply set the 'configs' parameter when building your form.

````
$formBuilder
    ->add('content', 'ckeditor', array('configs' => array( ... ));
````

Any parameters from here should work:
http://docs.cksource.com/ckeditor_api/symbols/CKEDITOR.config.html