nsqd: add max_msg_timeout and msg_timeout to IDENTIFY response
nsqd: add client configurable output buffering

* add --max-output-buffer-size command line option
* add --max-output-buffer-timeout command line option
nsqd: re-organize command line flags
add tests
Merge pull request #196 from mreiferson/flush_196

nsqd: client configurable output buffering