unix/async.py implements a poll-based socket loop.
epoll (Linux) is supported via python-epoll
library (http://sourceforge.net/projects/pyepoll).
kqueue/kevent (FreeBSD) and kpoll (Solaris) are not
supported yet.

Also it has more accurate and fast timers. A precision
of a timer is about 10 milliseconds (1 ms is a reality but
makes no much sense in our case). Timers are kept in a
new structure, so setting a timer has an O(log(N)) time
effort, and deleting a timer has now an O(1) time effort.

This module is recommended to use on UNIX-like systems
(POSIX systems with poll(2) support), especially on
heavy loaded Linux servers with epoll(4) enabled.