Allow passing of arguements to RMQ plugins

This change allows for the passing of plugin arguments for RMQ.  For example we're using it in conjunction with the priority plugin.

```ruby
require 'sneakers'

class Processor
  include Sneakers::Worker
  from_queue :priority_test , :arguments => {'x-max-priority' => 255}

  def work(msg)
    logger.info msg
  end
end
```