title: SailsJS and Mongo unique attribute is ignored
body: <p>I cant seem to get the unique attribute to actually check/validate for unique values while using Mongo in SailsJS.  I end up with identical usernames easily.  Any thoughts?  I checked the other post about this, but that was related to using Disk/Memory databases.</p>
  
  <p>Sails 0.10.x with sails-mongo@0.10.x</p>
  
  <p>Model:</p>
  
  <pre><code>module.exports = {
  
    attributes: {
      username:{
          type:'string',
          unique:true,
          required:true
      }
    }
  };
  </code></pre>
  
  <p>Connections.js config file</p>
  
  <pre><code>mongo: {
      adapter: 'sails-mongo',
      host: 'localhost',
      port: 27017,
      schema:true,
      migrate: 'safe',
      database: 'mydatabase'
  },
  </code></pre>