[Proposal][5.4] Add additional redis.connection alias

[hskrasek]

Now that the Illuminate Redis component roughly matches the same pattern as the Database component, I propose we add a redis.connection alias so that you don't have to inject or type hint the the entire RedisManager class.

$this->app->bind('redis.connection', function ($app) {
            return $app['redis']->connection();
        });

[taylorotwell]

Fine with me.