Add possibility to ignore custom paths via arguments

... as without it, one cannot fully use the tool and has to host his own version of script with ignored paths hardcoded, like here: https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/2.11/check_trailing_spaces.sh#L10

First, shall be implemented directly in PHP CS Fixer repo, to show it works properly, and then backported into this dedicated repo