sleep blocks forever after using sockets

I am not sure if this is really a bug, but it looks to me doesn't make sense:

``` ruby

require 'celluloid/io'

class C
  include Celluloid::IO
  def f
    print 'Sleep is fine '
    sleep 0.1
    puts 'here, '
    TCPSocket.new('example.com', 80)
    print 'but now it '
    sleep 0.1
    puts 'never reaches here.'
  end
end

C.new.f
# Sleep is fine here,
# but now it 
```

Thanks!