Use php-cs-fixer to automatically format our code

[pascalchevrel]

There is a great tool created by Fabien Potencier (creator of the Symfony framework) that automatically reformat your PHP code according to a set of code conventions.
By default they are Symfony code conventions but the tool is now a standalone one and it supports PSR and user contributed rules too now:

https://github.com/FriendsOfPHP/PHP-CS-Fixer

I tried it locally and it should help us keep consistency I think, I created a set of rules that reflect what we do in the project (basically PSR2 + most rules from symfony).

That means that once we are ready to provide a patch, we just have to go to the root of the project and type:

php-cs-fixer fix

And all the new code we have written will be fixed to follow our standards. Seems that it can also be hooked into Travis.

PR coming.