title: rails 3.2 migration cannot add index to create_table in change method
body: <p>here is my migration in rails 3.2.2:</p>
  
  <pre><code>class CreateStatistics &lt; ActiveRecord::Migration
    def change
      create_table :statistics do |t|
        t.string :name
        t.integer :item_id
        t.integer :value
        t.text :desc
  
        t.timestamps
        t.index [:name, :item_id]
      end
  
    end
  end
  </code></pre>
  
  <p>and here is the migrate error:</p>
  
  <pre><code>==  CreateStatistics: migrating ===============================================
  -- create_table(:statistics)
  ActiveRecord::ConnectionAdapters::TableDefinition
  rake aborted!
  An error has occurred, all later migrations canceled:
  
  undefined method `index' for #&lt;ActiveRecord::ConnectionAdapters::TableDefinition:0xbd16888&gt;
  
  Tasks: TOP =&gt; db:migrate
  (See full trace by running task with --trace)
  </code></pre>
  
  <p>what is the right way to create a index?</p>