Replace reduce method with sum function for rubyzip 3.0.0

Author: jochenehret

lib/cloud_controller/app_packager.rb

@@ -49,7 +49,7 @@ def fix_subdir_permissions(root_path, app_contents_path)
 
   def size
     Zip::File.open(@path) do |in_zip|
-      in_zip.reduce(0) { |memo, entry| memo + entry.size }
+      in_zip.entries.sum(&:size)
     end
   rescue Zip::Error
     invalid_zip!