title: TypeError occurs when trying to enable Mongo DB authentication
body: <p>I'm on <a href="http://docs.mongodb.org/manual/tutorial/enable-authentication/">step 3</a> of trying to enable Mongo DB authentication. When I try to create a user via the Mongo shell exactly as the directions indicate, the shell reports:</p>
  
  <p>TypeError: Property 'createUser' of object admin is not a function</p>
  
  <p>I started mongod with the --auth option and switched to the admin database. as always, help appreciated.</p>