more reliable dead connection reaping
more reliable dead connection reaping

gorilla websocket apparently returns nil even if writing timed out and
wrote 0 bytes.

so, check for pongs in a reasonable interval, and force reading so that
they show up.

simonjjones/atc,zachgersh/atc,pivotal-devin-fallak/atc,utako/atc,simonjjones/atc,utako/atc,pivotal-devin-fallak/atc,pivotal-devin-fallak/atc,simonjjones/atc,zachgersh/atc,zachgersh/atc,zachgersh/atc,savaki/atc,savaki/atc,utako/atc,savaki/atc