some testing code
update hiredis
a new dz_broker main loop, make all poller sockets in a single zmq_poll()
add a basic timer for local_capacity monitor and broadcast.

in Linux with timerfd support we use api from <sys/timerfd.h>. On other systems we use an attached thread running in the background and timing by POSIX sleep(3).
Merge pull request #4 from amyangfei/develop

new dzbroker mainloop and add a basic status timer