def set(stat, value, opts=EMPTY_OPTIONS)
      opts = {:sample_rate => opts} if opts.is_a? Numeric
      send_stats stat, value, SET_TYPE, opts
    end
def set(stat, value, opts=EMPTY_OPTIONS)
      opts = {:sample_rate => opts} if opts.is_a? Numeric
      send_stats stat, value, SET_TYPE, opts
    end
Sends a value to be tracked as a set to the statsd server.

 @param [String] stat stat name.
 @param [Numeric] value set value.
 @param [Hash] opts the options to create the metric with
 @option opts [Numeric] :sample_rate sample rate, 1 for always
 @option opts [Array<String>] :tags An array of tags
 @example Record a unique visitory by id:
   $statsd.set('visitors.uniques', User.id)