*: add wal
main: use data-dir as the path to data directory flag
main: better error msg
main: add a helper function for starting raft
main: use -> using
wal: clarify TODO
main: check the id read by from wal.
wal: named return values for ReadAll.
wal: change entries->ents for consistency
main/wal: add a const for 0700 magic number
raft: refactor restart test
main: make default data to have _data_etcd suffix
raft: fix the comment in test
main: clarify fatal message for unexpect nodeid
Merge pull request #992 from coreos/wal

wal