added cfg.reconnect to allow the page in a child frame to reconnect with its parent after a reload

Hi, I noticed that a channel looses its connection if the page in the child frame is reloaded. 

Needed to be able to "reconnect" with the parent again after navigating inside the iframe, so here's a take on that functionality. A demo can be found under `example/multipage/`. 

Would be great to get some input on this functionality... There's probably a safer and better way to do it. (On that note, the real use case does not use `origin: "*"`)