title: eb: error: unrecognized arguments: --database.engine.version
body: <p>According to the AWS EB documentation for <a href="http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/eb3-create.html" rel="nofollow"><code>eb create</code></a>, I should be able to create an elastic beanstalk environment with an postgres database, via this command:</p>
  
  <pre><code>eb create myapp-env --database.engine.version postgres-9.4.1                                                                                        
  usage: eb {cmd} &lt;environment_name&gt; [options ...]
  eb: error: unrecognized arguments: --database.engine.version postgres-9.4.1
  </code></pre>
  
  <p>I've also tried these command line arguments to no avail:</p>
  
  <pre><code> eb create myapp-env -db.engine postgres --database.engine.version 9.4.1 
  </code></pre>
  
  <p>Any help is appreciated!</p>