title: Rails and jsonb type "jsonb" does not exist
body: <pre><code>psql --version
  psql (PostgreSQL) 9.4.1
  
  rails -v
  Rails 4.2.0
  </code></pre>
  
  <p>I added a jsonb column through migration like that </p>
  
  <pre><code>class AddPreferencesToUsers &lt; ActiveRecord::Migration
    def change
      add_column :users, :preferences, :jsonb, null: false, default: '{}'
      add_index :users, :preferences, using: :gin
    end
  end
  </code></pre>
  
  <p>I get this error :</p>
  
  <pre><code>PG::UndefinedObject: ERROR:  type "jsonb" does not exist
  LINE 1: SELECT 'jsonb'::regtype::oid
  </code></pre>
  
  <p>any help ?</p>