nsqd: make max heartbeat interval configurable
bump to 0.2.20-alpha
Merge pull request #178 from mreiferson/config_max_heartbeat_178

nsqd: configurable max heartbeat interval
docs: updated protocol.md missed in #158
nsqd: allow configurable max heartbeat interval
go-nsq: RDY state updates:

* bootstrap RDY count to 1
* use feature negotiation to get server max RDY count
* never send RDY count > server max RDY count
Merge pull request #175 from mreiferson/config_rdy_175

nsqd: allow configurable max RDY count
bump go-nsq v0.3.2-alpha; update ChangeLog
docs: add mention of feature_negotiation to IDENTIFY
init add writer