add bitstreams to learning object

db/migrate/20160125120915_create_learning_objects.rb

@@ -11,6 +11,7 @@ class CreateLearningObjects < ActiveRecord::Migration
       t.integer :school_level
       t.string :language
       t.text :metadata
+      t.text :bitstreams
       t.text :keywords
 
       t.references :published, polymorphic: true, index: true