Update symfony_integration.md

Hi, Benjamin.
I have pushed PorpaginasBundle. As I understand, porpaginas doesn't work with pagerfanta. There are a some conflicts:

[PagerfantaRenderingAdapter.php#L40-L42](https://github.com/beberlei/porpaginas/blob/master/src/Porpaginas/Twig/PagerfantaRenderingAdapter.php#L40-L42) and [PorpaginasAdapter.php#L12](https://github.com/beberlei/porpaginas/blob/master/src/Porpaginas/Pagerfanta/PorpaginasAdapter.php#L12).

Furthermore, there are two undefined classes. https://github.com/beberlei/porpaginas/blob/master/src/Porpaginas/Twig/PagerfantaRenderingAdapter.php#L42

But library and knp_paginator works fine. We have started to use it.