raft: return offset for unstableEnts
etcd: add version handlers
Merge pull request #16 from etcd-team/version

etcd: add version handler
wal: init
wal: make new work
wal: add tests for write
raft: add Load
wal: check written data in tests
wal: add Read
wal: cleanup
wal: use buffer
wal: add newWal helper func
raft: refactor recover
wal: add CoreOS copyright
wal: reorgnize wal file
wip: wal glue
etcd: add destoryCluster for testing
etcd: use tmpDir as testing directory
server: save correct nodeId for participant
server: apply ents when loading log