Allow queue to be switched based on tag/data

[colinnewell]

I had hoped to switch queue based on tag like this,

 queue_name "#{ENV['BASE_SQS_URL']}${tag[1]}"

The ENV var got correctly interpolated, but the tag wasn't. This might be down to me not understanding the fluentd config format correctly, but I suspect the code simply doesn't support this type of data currently.

If I'm reading the code right, I suspect it would need something like a call to extract_placeholders in order to deal with tags in the data, with possibly some slightly more structural changes to the module.