title: Why can't I update to the latest MongoDB with Homebrew?
body: <p>I have version 2.0.2 of mongo installed on my mac, which I installed using Homebrew. The course I'm taking is using the 'aggregate' function, which is only available in version 2.2 of Mongo.  I tried to do </p>
  
  <pre><code> brew upgrade mongodb
  </code></pre>
  
  <p>and I get   </p>
  
  <pre><code>Error: mongodb already upgraded
  </code></pre>
  
  <p>Is there a way to install the latest version of Mongo with Homebrew?</p>