Make symfony/console 3.2.0 minimal requirement

[tuupola]

The Symfony\Component\Console\Terminal class is not available before 3.2.0. This breaks the builds using --prefer-lowest switch. This can also be tested locally from phplint source tree with:

$ composer update --prefer-lowest
$ bin/phplint

 PHP Fatal error:  Uncaught Error: Class 'Symfony\Component\Console\Terminal' not found in /xxx/phplint/src/Command/LintCommand.php:249

Setting to symfony/console minimum requirement to ^3.2 seems to fix the problem.

[overtrue]

Thanks.