adds moderation to comments and debates [#136]

db/migrate/20150810201448_add_hidden_at_to_comments.rb

@@ -0,0 +1,6 @@
+class AddHiddenAtToComments < ActiveRecord::Migration
+  def change
+    add_column :comments, :hidden_at, :datetime
+    add_index :comments, :hidden_at
+  end
+end

db/migrate/20150811145628_add_hidden_at_to_debates.rb

@@ -0,0 +1,6 @@
+class AddHiddenAtToDebates < ActiveRecord::Migration
+  def change
+    add_column :debates, :hidden_at, :datetime
+    add_index :debates, :hidden_at
+  end
+end