title: Throttling ChannelGroup in Netty
body: <p>There's <code>GlobalChannelTrafficShapingHandler</code> that allows me to shape traffic for each <code>Channel</code>s and globally. </p>
  
  <p>Is there a way of throttling a group of channels, for example captured in <code>ChannelGroup</code>?</p>
  
  <p>So that I can have multiple <code>ChannelGroup</code>s and apply different throttling policy to each?</p>