raft: protobuf messageType
Merge pull request #1293 from unihorn/160

raft: protobuf messageType
etcdserver: change machines endpoint to members
Merge pull request #1290 from coreos/member_endpoint

etcdserver: change machines endpoint to members
etcdserver: clean NewServer
etcdserver: add shouldDiscover
etcdserver: add s.apply
etcdserver: Id -> ID
etcdserver: fix typo
Merge pull request #1288 from coreos/cleanup

etcdserver: clean NewServer
raft: add RemovedNodes to SoftState
raft: add ConfChangeNil
etcdserver: add checking when apply conf change
etcdserver: rename to containsUint64
Revert "raft: add ConfChangeNil"

This reverts commit 1c934ef030e731c678d37225fbe2312cd962936f.
etcdserver: use none nodeID to indicate invalidation