Add support for Modules commands

[gkorland]

Modules commands' names are usually in the format XXX.YYY. Which means the command name includes . after the prefix.

[pavelsr]

+1. E.g. I need to execute JSON.SET from RedisJSON but no way with Perl client lib.

[pavelsr]

Btw, you can execute module commands even now via __std_cmd, e.g.

Redis->new( server => 'redis:6379' )->__std_cmd('JSON.SET', $mem_key, '.', encode_json($data) );

[dams]

This is related to https://github.com/PerlRedis/perl-redis/pull/137