output capture stats

[Phillipmartin]

build in an optional capture stats output stream. something that works with statsd.

[Phillipmartin]

we'll use gopassivedns... as our namespace pattern, where thread is optional.

Metrics to log will be:

number of lookups (Increment)
size of connection cache tables (Gauge)
number of flushed connection table entries (Increment)
size of packet queue (Gauge)
size of tcp queue (Gauge)
size of log queue (Gauge)