Feature Request - support with :trail

Hi there,
I see there is a parameter `options[:trail]` right here in [ConsumerGroup](https://github.com/bsm/poseidon_cluster/blob/17f372ff2c351841f84eecd88774785386f244b5/lib/poseidon/consumer_group.rb#L94). Which is used to skip all the old messages in a specific topic. It's very useful if you want to consume an existing topic from the latest.

I would like to have it supported here in fluent plugin.