require logger, as it is not required by concurrent-ruby < 1.3.5

Author: toy

spec/image_optim/railtie_spec.rb

@@ -3,6 +3,7 @@
 require 'spec_helper'
 require 'rails/all'
 require 'image_optim/railtie'
+require 'logger'
 
 describe 'ImageOptim::Railtie' do
   def rails_app