title: Ability to tag friends in a facebook native share dialogue
body: <p>I am using the Facebook iOS SDK 3.1 in my latest, and I'm using the native share dialogue from <code>FBNativeDialogue</code>.</p>
  
  <p><img src="https://i.stack.imgur.com/q1GBz.png" alt="enter image description here"></p>
  
  <p>It has a "friends" button in the corner, which I always throught was to tag friends (just like the location button tags the location), but I realised that this is privacy settings for the post.</p>
  
  <p>Therefor, Im still confounded how you can tag friends in a post. Nothing seems to happend when i type @ followed by my friends names, is this not implemented yet ? And does anyone know of clever way to implement this ?</p>
  
  <p>What the customer wants is the similar to the "Who are you with?" button as shown here:</p>
  
  <p><img src="https://i.stack.imgur.com/UGudQ.png" alt="enter image description here"></p>