Bump celluloid-io dependency to 0.13.1
Bump celluloid-io dependency to 0.13.1

This should fix a problem with improper handling of prematurely closed
connections. There was a bug where, if ringleader hadn't yet gotten around to
proxying a socket before it was closed, an IOError would be raised from within
celluloid itself, and it was impossible to rescue from this situation.

zerowidth/ringleader,zerowidth/ringleader,zerowidth/ringleader