Add support for predis v2

[senaranya]

Updating predis to ~v2 in composer.json fails the tests with:

PHP Fatal error:  Declaration of M6Web\Component\RedisMock\RedisMock_Predis_Client_Adapter::pipeline($arguments) must be compatible with Predis\Client::pipeline(...$arguments) in /var/www/html/scriptsender/vendor/m6web/redis-mock/src/M6Web/Component/RedisMock/RedisMockFactory.php(226) : eval()'d code on line 40

[Oliboy50]

thanks for your time

as you said, it seems to have been fixed in #108