FEATURE: Create a rake task for destroying categories

Created a rake task for destroying multiple categories along with any
subcategories and topics the belong to those categories.

Also created a rake task for listing all of your categories.

Refactored existing destroy rake tasks to use new logging method, that
allows for puts output in the console but prevents it from showing in
the specs.

lib/tasks/categories.rake

@@ -36,3 +36,11 @@ end
 def print_status(current, max)
   print "\r%9d / %d (%5.1f%%)" % [current, max, ((current.to_f / max.to_f) * 100).round(1)]
 end
+
+desc "Output a list of categories"
+task "categories:list" => :environment do
+  categories = Category.pluck(:id, :slug, :parent_category_id)
+  categories.each do |c|
+    puts "id: #{c[0]}, slug: #{c[1]}, parent: #{c[2]}"
+  end
+end