doc: add doc for proxy
integration: add basic discovery tests
Merge pull request #1670 from yichengq/207

integration: add basic discovery tests
etcdmain: actually return errors
Merge pull request #1680 from jonboulle/fix_errors

etcdmain: actually return errors
doc: add fallback to discovery section in clustering.md
etcdmain: do not exit inappropriately
Merge pull request #1681 from jonboulle/fix_exit

etcdmain: do not exit inappropriately
Merge pull request #1671 from xiang90/proxy_doc

doc: add doc for proxy
proxy: return JSON errors
proxy: add a todo for logging
Merge pull request #1685 from xiang90/proxy

proxy: return JSON errors
integration: rewrite the way to check cluster make progress
integration: newMember -> mustNewMember
Merge pull request #1682 from yichengq/217

integration: rewrite the way to check cluster make progress
raftpb: fix proto
Merge pull request #1686 from xiang90/proto

raftpb: fix proto
*: support update peerurl