Add attr_reader :wait to RotationRequest.

RotationRequest should have :wait attr_reader.
Because the following line exists in in_tail.rb:232.

  wait -= @rotate_queue.first.wait unless @rotate_queue.empty?
Merge pull request #118 from mokemokechicken/fix_RotationRequest_mokemokechicken

Add attr_reader :wait to RotationRequest.