title: rake db:migrate does nothing
body: <p>I'm following this <a href="http://guides.rubyonrails.org/getting_started.html" rel="nofollow">tutorial</a>, 
  and I'm having a problem when running <code>rake db:migrate</code></p>
  
  <p>In <code>db/migrate</code> I have the <code>create_post.rb</code> file:</p>
  
  <pre><code>class CreatePosts &lt; ActiveRecord::Migration
    def change
      create_table :posts do |t|
        t.string :title
        t.text :text
        t.timestamps
      end
    end
  end
  </code></pre>
  
  <p>But it does not create the table.
  My <code>database.yml</code> file is:</p>
  
  <pre><code>development:
   adapter: mysql2
   encoding: utf8
   database: blog_development
   pool: 5
   username: root
   password:
   socket: /tmp/mysql.sock
  </code></pre>
  
  <p>The output from rake <code>db:migrate</code> seems ok. </p>
  
  <p>I'm using <code>phpMyAdmin</code> to handle the database, which is correctly created manually by me. </p>
  
  <p>What am I doing wrong?</p>