title: Django SwampDragon : KeyError 'channel'
body: <p>I have searched everywhere for a solution on this and after a long time searching I still have no answer.</p>
  
  <p>I am using Django 1.7 over Swampdragon 0.4.2. I get this exception every random period of time.</p>
  
  <pre><code>WebSocket
  Traceback (most recent call last):
    File "/usr/local/lib/python2.7/site-packages/sockjs/tornado/transports/websocket.py", line 60, in on_message
      self.session.on_messages(msg)
    File "/usr/local/lib/python2.7/site-packages/sockjs/tornado/session.py", line 418, in on_messages
      self.conn.on_message(msg)
    File "/usr/local/lib/python2.7/site-packages/swampdragon/connections/sockjs_connection.py", line 90, in on_message
      raise e
  KeyError: 'channel'
  
  Request repr(): unavailable
  </code></pre>
  
  <p>Anybody has any idea why this is?</p>