title: Multiple foreign keys referencing the same table in RoR
body: <p>I want a Customer to reference two Address models, one for the billing address and one for the shipping address.  As I understand it, the foreign key is determined by its name, as _id.  Obviously I can't name two rows address_id (to reference the Address table).  How would I do this?</p>
  
  <pre><code>create_table :customers do |t|
    t.integer :address_id
    t.integer :address_id_1 # how do i make this reference addresses table?
    # other attributes not shown
  end</code></pre>