nsqd: HTTP versioning

* drop response wrapper
* use correct HTTP codes
* use Accept header to indicate version
nsqd: require post for mutating v1 HTTP endpoints
Merge pull request #330 from mreiferson/http_refactor_330

nsqd: http api inconsistencies
bump go-nsq to v1.0.0-alpha
apps: convert to new go-nsq API
util: copy some methods from go-nsq
nsqd: dont depend on go-nsq for non-client functions
bench: refactor for new go-nsq API
nsqadmin: dont depend on go-nsq
nsqlookupd: dont depend on go-nsq