title: Custom cell for JSQMessages
body: <p>I'm attempting to create a custom message cell that has an icon (on the right hand side for incoming and left hand side for outgoing)</p>
  
  <p>I've subclassed <code>JSQMessagesCollectionViewCellOutgoing</code> and have the icon displayed where I want. great. What I haven't been able to do is have the Text View's width smaller to take into account the icon. I thought it was a simple autolayout change in my custom outgoing xib file, but when the app runs, the autolayout width is overridden. </p>
  
  <p>How do I update (directly or indirectly) <code>textViewMarginHorizontalSpaceConstraint</code> within <code>JSQMessagesCollectionViewCell</code> from a subclass of either <code>JSQMessagesCollectionViewCell</code> or <code>JSQMessagesCollectionViewCellOutgoing</code></p>