Add contactable to tracks

Added social media fields to track submission form
by using a polymorphic association with the
Contact Model.

db/migrate/20190612161235_add_polymorphic_to_contact.rb

@@ -0,0 +1,6 @@
+class AddPolymorphicToContact < ActiveRecord::Migration[5.1]
+  def change
+    add_column :contacts, :contactable_type, :string
+    add_column :contacts, :contactable_id, :integer
+  end
+end