migration to add avatar to institutions

db/migrate/20170503134230_add_attachment_avatar_to_institutions.rb

+class AddAttachmentAvatarToInstitutions < ActiveRecord::Migration
+  def self.up
+    change_table :institutions do |t|
+      t.attachment :avatar
+    end
+  end
+
+  def self.down
+    remove_attachment :institutions, :avatar
+  end
+end