Addition of statsd support and several usability improvements

Bug Fixes

• "Status" keys from ppagent now expire properly
• Graceful shutdown now flushes queued "one minute shares" properly

Features

• Optional "events" config value sends various helpful performance stats to a statsd endpoint over UDP
• Blocking detector logs traceback when gevent hasn't context switched in 1 second
• Monitor views are substantially expanded to include more information
• Mining client version is now recorded on client object
• Added a minimum manual share difficulty setting
• Pool shares can now be reported in several very flexible ways
• All port numbers will now be based off of a "server_number" which is now a command line option as well, making clustering much easier