optimization in sendnl routing
added 'uwsgi' transformation
transformation_template has been moved to a plugin
added no_content_length to the cache router
added better random initialization and rr/rand hash algos
implemented #284
busy_workers and idle_workers must be GAUGE
use uwsgi.start_tv for srand instead of recomputing it
completed metric threshold subystem
do not destroy the stats pusher loop on EINTR
added stats pusher default plugins
metrics as objects in stats subsystem