Exceptions shouldn't be used with EventMachine

There is no way(or I don't know it) gracefully continue EM loop after raising an exception inside.
Moreover there is nothing happened here. Just close the connection and if it's required there is an ability to overlap unbind method to react on it.
This patch helps me to run multiple Blather clients in a single EM loop and restart them on connection failure.

```ruby
disconnected do
   EM::add_timer(15){ self.run }
end
```