Merge pull request #35 from hintjens/master

Updated NEWS for release 4.0.2
Merge pull request #36 from hintjens/master

Updated version number for 4.0.2
Merge pull request #37 from hintjens/master

Fixed test_many_sockets
Merge pull request #40 from hintjens/master

Backported fix for #763
use enum retired_fd instead of -1

using -1 causes a warning on Windows platform because SOCKET is unsigned.
Updated news for #775