Apply the changes of the english version

The english version has been edited according to the changes in the 2.3 version of Symfony about the PropertyPath and the FormView classes. The previous code was not working anymore.

I used the code from here:
http://symfony.com/doc/master/cookbook/form/create_form_type_extension.html
Merge pull request #306 from ValentinH/patch-1

Apply the changes of the english version